5.2 Electron Configuration and the Periodic Table

Summary

This video explores Chapter 5, Section 2 on electron configuration and the periodic table. It explains how the periodic table is organized into groups and periods based on elements' electron configurations and energy levels. The video covers key concepts like noble gases, the octet rule, and the division of the table into s, p, d, and f blocks. It also highlights the reactivity of elements in different blocks, such as alkali metals, halogens, and transition metals, and touches on synthetic elements in the actinides group.

Takeaways

• 📚 The video covers electron configuration and its relation to the periodic table, focusing on Chapter 5, Section 2.
• 🌌 Scientists discovered additional elements later on that were challenging to categorize, leading to the identification of noble gases due to their full outer electron shell, making them unreactive.
• 🔍 The periodic table is arranged to reflect recurring chemical properties, with elements sharing common traits placed in vertical columns called groups.
• 📏 The table is also divided horizontally into periods, with each period's length indicating the number of electrons that can occupy the sublevels within that period.
• 🧲 Elements' electron configurations determine their position and period on the periodic table, such as arsenic (element 33) which is in the fourth period due to its highest energy level.
• 📖 The periodic table is divided into blocks (S, P, D, F) based on the subshell (s, p, d, f) being filled for the elements within them.
• 🔋 S-block elements, including alkal metals and alkaline earth metals, are highly reactive metals with electron configurations of ns^1 and ns^2, respectively.
• 🌉 D-block elements, or transition metals, are found between groups 3 and 12 and are less reactive than S-block metals, with some even found in nature in their free state.
• 💠 P-block elements are the main group elements, characterized by having a full s orbital and varying numbers of valence electrons, leading to a diverse range of properties including metals, metalloids, and non-metals.
• ⚛️ The halogens in group 17 of the P-block are highly reactive non-metals with seven valence electrons, always seeking to complete the octet.
• 🧪 Lanthanides and actinides in the F-block are placed at the bottom of the periodic table and are synthetic, radioactive elements created in laboratories.

Q & A

Why are noble gases unreactive?

Noble gases are unreactive because they follow the octet rule completely, having a full outer shell of electrons, which makes them chemically stable.

What determines an element's chemical properties?

An element's chemical properties are determined by its valence electrons, also known as the outermost shell of electrons.

How are elements with common properties arranged in the periodic table?

Elements with common properties are arranged into columns called groups in the periodic table.

What is the significance of the periodic table's horizontal arrangement into periods?

The horizontal arrangement into periods indicates the number of electrons that can occupy various sublevels within that period.

Why does the first period of the periodic table only contain two elements?

The first period contains only hydrogen and helium, which can only hold two electrons in the 1s sublevel, hence it has two elements.

How does an element's electron configuration give its period and location on the periodic table?

An element's electron configuration, particularly the highest energy level and sublevel occupied by electrons, determines its period and group on the periodic table.

What are the P, S, D, and F blocks in the periodic table, and what do they represent?

The P, S, D, and F blocks represent groups of elements where specific sublevels (p, s, d, f orbitals) are being filled. These blocks categorize elements based on the type of orbitals being filled in their electron configurations.

Why are group 1 elements called alkali metals and group 2 elements called alkaline earth metals?

Group 1 elements are called alkali metals and group 2 elements are called alkaline earth metals due to their tendency to lose one and two electrons easily, respectively, which is characteristic of their chemical reactivity.

How do you determine the number of valence electrons for main group elements in the P block?

For main group elements in the P block, the number of valence electrons is typically the group number minus 10.

Why are halogens the most reactive non-metals in the periodic table?

Halogens are the most reactive non-metals because they have seven valence electrons, which is one electron short of the stable octet configuration, making them highly reactive to achieve stability.

What are the lanthanides and actinides, and why are they placed at the bottom of the periodic table?

The lanthanides and actinides are series of elements with similar properties to the rare earths, placed at the bottom of the periodic table to save space and because they fill the f orbitals. They are similar and were difficult to distinguish, and many are synthetic, created in laboratories.

Outlines

00:00

🔬 Electron Configuration and the Periodic Table

This paragraph introduces Chapter 5, Section 2, which focuses on electron configuration and its relation to the periodic table. The discovery of additional elements that were challenging to categorize led to the identification of the noble gases, characterized by their full outer electron shells, or octets, which make them unreactive. The periodic table's arrangement is explained, with elements sharing common properties grouped into columns called groups. The periodic table also divides elements into periods based on the number of electrons that can occupy sublevels within each period. The electron configuration of an element, such as arsenic, determines its position on the table. The table is further divided into blocks (P, S, D, F) based on the sublevel being filled, with each block having distinct characteristics and properties.

05:01

🔋 The S and D Blocks of the Periodic Table

This section delves into the S and D blocks of the periodic table. The S block includes the alkal metals (group 1) and alkaline earth metals (group 2), which are highly reactive due to their tendency to lose electrons easily. Hydrogen and helium, despite following the ns1 and ns2 configurations, are chemically distinct and not typically classified with the S block elements. The D block, comprising groups 3 through 12, is characterized by the filling of d orbitals. The energy levels and the order of filling these orbitals are discussed, with a focus on how the D block elements, or transition metals, are less reactive than the S block and can sometimes be found in their elemental form in nature.

10:02

🌐 The P Block and Main Group Elements

The P block, which includes groups 13 through 18, is explored in this paragraph. All elements in the P block have a full s orbital, and the number of valence electrons is determined by subtracting 10 from the group number. The P block is diverse, containing metals, metalloids, and non-metals, and is crucial for understanding main group chemistry. Metalloids, a subset of the P block, are semiconductors with conductivity between metals and non-metals. The halogens, found in group 17, are the most reactive non-metals due to having seven valence electrons, making them highly susceptible to chemical reactions to achieve a stable octet. The paragraph concludes with a brief overview of the F block, which includes the lanthanides and actinides, and their unique characteristics, such as being radioactive and synthetically created.

Keywords

💡Electron Configuration

Electron configuration refers to the arrangement of electrons around the nucleus of an atom. It is a fundamental concept in chemistry that determines an element's chemical properties and reactivity. In the video, electron configuration is used to explain how elements are positioned in the periodic table, with the outermost electrons, or valence electrons, being particularly important for chemical bonding and reactions. For example, the video discusses how the noble gases follow the octet rule, having a full outer shell of electrons, making them unreactive.

💡Periodic Table

The periodic table is a tabular arrangement of chemical elements organized by atomic number, electron configuration, and recurring chemical properties. It is a visual representation of the periodic law, which states that the properties of the elements are periodic functions of their atomic number. The video script explains how the periodic table is laid out, with elements of similar properties arranged into groups and periods, and how this arrangement helps in understanding the electron configurations of elements.

💡Noble Gases

Noble gases are a group of chemical elements in Group 18 of the periodic table, which are known for their lack of reactivity. They are characterized by having a full valence electron shell, which makes them stable and unreactive. In the script, noble gases are mentioned as an example of elements that follow the octet rule completely, which is why they are positioned on the far right of the periodic table.

💡Octet Rule

The octet rule states that atoms of main-group elements tend to combine in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas. This rule is crucial for understanding chemical bonding. The video script uses the octet rule to explain why noble gases are unreactive and why elements in other groups seek to achieve this stable electron configuration through chemical reactions.

💡Valence Electrons

Valence electrons are the electrons in the outermost electron shell of an atom. They play a crucial role in determining an element's chemical properties because they are the ones involved in chemical bonding. The video emphasizes the importance of valence electrons by explaining how they dictate an element's reactivity and position within the periodic table.

💡Groups and Periods

Groups (also known as families or columns) and periods (rows) are the organizational units of the periodic table. Elements in the same group have similar chemical properties, while elements in the same period have the same number of electron shells. The video script discusses how the periodic table is arranged into groups and periods, with groups reflecting similarities in chemical behavior and periods reflecting the number of electron shells.

💡Sublevels

Sublevels, also known as electron shells or orbitals, are regions in an atom where electrons are most likely to be found. The video script explains that the length of each period in the periodic table corresponds to the number of electrons that can occupy various sublevels within that period. For instance, the first period contains only hydrogen and helium, which have one s sublevel, while subsequent periods include more sublevels like s and p, which can hold more electrons.

💡S Block

The S block in the periodic table includes elements that have their highest energy electrons in s orbitals. This block contains the alkali metals and alkaline earth metals, which are highly reactive due to their tendency to lose electrons easily. The video script mentions that hydrogen and helium, despite having s orbitals, are not typically included in the S block with the alkali and alkaline earth metals due to their differing chemical properties.

💡D Block

The D block elements are transition metals found in groups 3 through 12 of the periodic table. They are characterized by having partially filled d sublevels. The video script explains that the D block elements are less reactive than the S block metals and are found between the highly reactive alkali and alkaline earth metals and the P block metals. The electron configurations of D block elements are described as having a pattern of filling the s orbital first before filling the d orbitals.

💡P Block

The P block elements are found in groups 13 through 18 and include metals, metalloids, and non-metals. They are characterized by having a full s orbital and varying numbers of electrons in the p orbitals. The video script discusses the diversity within the P block, including the presence of halogens, which are highly reactive non-metals due to having seven valence electrons, just one short of the stable octet configuration.

💡F Block

The F block consists of the lanthanides and actinides, which are placed at the bottom of the periodic table to save space. These elements have their electrons in the f sublevels, which are filled in a complex manner. The video script mentions that the lanthanides and actinides are similar in their properties, and many of them are synthetic, having been created in laboratories rather than occurring naturally.

Highlights

Introduction to Chapter 5 Section 2 focusing on electron configuration and its relation to the periodic table.

Explanation of the discovery of noble gases and their unreactivity due to following the octet rule.

Discussion on how the outer shell of electrons, known as valence electrons, determines an element's chemical properties.

Description of the periodic table's organization into groups and periods based on electron configurations.

Explanation of how the length of periods in the periodic table corresponds to the number of electrons that can occupy sublevels.

Detail on how the electron configuration of an element like arsenic determines its period and position on the periodic table.

Division of the periodic table into subblocks: P, S, D, F, and their significance in electron filling.

Explanation of S-block elements, including alkal metals and alkaline earth metals, and their reactivity.

Distinction between hydrogen and helium despite following ns1 and ns2 configurations, due to their differing chemical properties.

Introduction to D-block elements, their position in the periodic table, and their transition metal properties.

Clarification on the electron configuration notation for D-block elements and the significance of the 4S being lower energy than 3D.

Overview of P-block elements, their full s orbital, and their categorization as main group elements.

Importance of valence electrons in main group elements and the method to determine them by subtracting 10 from the group number.

Diversity within the P-block, including metals, metalloids, and non-metals, and their distinct properties.

Discussion on metalloids as semiconductors with conductivity between metals and non-metals.

Explanation of the halogens in group 17 as the most reactive non-metals due to having seven valence electrons.

Brief overview of the F-block elements, the lanthanides and actinides, their positions on the periodic table, and their synthetic nature.

Transcripts

so in this video we're covering chapter

5 Section two which is electron

configuration and the periodic table now

as I mentioned in the last chapter um

when they laid out the periodic table uh

scientists found some extra elements

later on that were very hard to

categorize and this was because they

were highly

unreactive and they are a group over

here known as the noble gases and the

noble gases are unreactive because they

follow something called the octet rule

completely which

is where your entire outer uh shell of

electrons is

full and what you'll find is that this

outer shell of electrons often called

the veence

electrons is what determines an elements

chemical properties so as I mentioned in

my last video

um the table is arranged so that you

periodically come across elements of the

same properties and these elements with

common properties are put into columns

called groups for example this is group

one and over here you

have group

18 and what this means is that the

vertical elements in each of these share

uh various properties however it's also

arranged horizontally into what are

known as

periods now the length of each of these

periods shows the number of electrons

that can occupy various sublevels within

this period for example the first period

which contains only hydrogen and helium

has two elements in it therefore it can

only hold two electrons in this case in

the

1s uh suev now if you look at the next

one down it has eight elements in it and

that's because it contains the sublevels

2 s and 2 p which as we learned

previously the S orbital Su can hold two

electrons and the P can hold

six now if you move further down you'll

notice that this

has 10 more in the

middle which means that in total this

period can hold

18 and so on and so forth you get down

to the sixth and seventh periods when

you add 14 more with the lanides and

actinides and you get that period with

all its Su levels included can hold up

to

32 uh electron Arrangements meaning 32

different elements an elements electron

configuration also gives its period and

location on the table for example let's

take say uh element 33 arsenic now

arsenic if we use the noble gas notation

has the electron

configuration argon 3

d10 4 S to 4

P3 now as you'll notice the highest

energy level that argon has electrons in

is the

fourth and non-

coincidentally uh it is in the fourth

period now you'll also notice that the

highest suev that electrons and argon

occupy is the p suble right

here and that is the same for all of

these

elements in what is known as the P block

now this is common practice the table is

divided into a few what are known as

sort of subblocks of the table now I'll

start over here first this is the P

block and then you if you come back over

here to the alkal metals and the alkal

earth metals they form what is known as

the S block along with uh hydrogen and

helium which as we know have one s one

and two which is why they're in the S

block because their highest suble is s

then the middle we have the D

Block these are a bunch of transition

metals which we'll study later and then

finally down at the bottom the

lanthanides and actinides form the F

block and these blocks all derive their

name based on which Su is being filled

uh at that point for these elements so

now we'll take a closer look at the s s

block elements now the X X block

elements are the elements from group one

and group two which tend to be highly

reactive metals now their electron

configurations are

ns1 and

ns2 respectively where n is the energy

level because obviously they're not all

in the same energy level that's why

they're in different periods now the

ease which with with which uh the group

one elements lose this one electron

right here is what makes them highly

reactive group two also is highly

reactive because it's pretty easy to

lose these two electrons as

well uh now they have special names

group one is called the alkaline

metals and group two very

similarly is called the

alkaline earth

metals now although hydrogen and helium

follow these two configurations of ns1

and ns2 with one with the first energy

level they're not usually included in

like the main s block with the alkaline

metals and the alkaline earth metals

because they're very chemically

different they aren't as reactive so

they don't have to be stored under oil

like these do to avoid uh explosive

reactivity so now we're going to be

looking at the dblock elements which

form groups 3 through 12 and if you'll

remember from our rules earlier for each

energy level n which is uh one of our

quantum numbers uh then there are N Sub

levels so what that means is that once

you get down to the third energy level

you now have suble levels s p and d you

have three of

them

now you may be saying to yourself okay

so why the third period if that

corresponds to the energy level aren't

there a block of dgroup elements and

that is

because the D

suev actually is a slightly higher

energy than the sub suevel of the next

energy level so what I'm saying is that

if the 4S energy level uses say this

much energy then the 3D is slightly up

and if we follow our diagonal lines as

we did earlier you see that you have to

fill up the lower energy

4S uh level before you fill up the 3D so

the D suevel has a total of five

orbitals which can hold up to two

electrons

each if you'll remember you can have up

to two electrons in each of these

sublevels so the grand total of electron

Arrangements in the D suble comes out to

10 which is why there are 10 elements

here in the DB block across now because

of the weird energy states where 4S is

lower energy than

3D the formula notation for d block

elements is a bit

strange so if we were to take uh

Scandium for example its electron

configuration would be

argon uh

3d1

4S 2 because you still go in order of

ascending energy level despite the fact

that the 4S orbital is slightly lower

energy than the 3D but this means that

the formula generally is n minus one or

n is the period or highest energy level

D however many so

DX uh four or sorry n S2 so basically

what this means is that you take the

energy level you're at and fill up that

s orbital first and then what you'll do

is you fill up the D orbital with

however many across you're

going uh based on the energy level

before it now DB block elements are as

you can see often called transition

metals and this is because they're

between the highly

reactive Alkali and alkaline earth

metals and the P block Metals over here

on the right and they are so much less

reactive than the S block metals

that they are even occasionally found in

nature as uh lone elements such as gold

or platinum or silver is also found in

nature occasionally free so now we'll

look at the P block which makes up uh

groups 13 through 18 and first thing you

have to know is that the P block every

single element has a full s orbital so

all of their s orbitals have two

electrons in them already and the next

thing you need to know is that the P

block over

here along with the S block which we can

also see on this uh shortened table form

what are known as the main group

elements and the main group elements are

the ones we're going to be studying for

most of this course uh with some

dabbling into d block but certainly not

F block

chemistry now an important number to

know for all elements on the table but

especially for the main group elements

that we're going to be working with is

the number of veence

electrons that each element has and the

veence electrons are simply the ones in

the outermost energy level and it's

really simple for the P block elements

you just take the group number in this

case let's say for Boron aluminum

gallium and indium uh 13 and then you

subtract

10 and what you end up with is three

that the correct number of veence

electrons because as you can see they

fill up the uh 2s orbital and then

there's one electron in the 2p orbital

cuz this uh P block over here follows

the arrangement of uh

ns2 NP however Benny in this case np1 2

3 four five and six when you get all the

way over to the noble gases and this

rule of subtracting 10 from the group

number works for all the elements in the

P block for example if you were to take

carbon and do 14 minus 10 you would get

that it has four veence electrons which

is the correct number and then as you

can see from this chart and the various

colors uh the P block is probably the

most diverse block on the table as far

as uh categorizing the actual elements

within it it contains metals metalloids

and

non-metals now I'm sure most of you

understand uh some of the properties of

metals conductivity luster Etc and

probably some of non-metals as well uh

such as oxygen and nitrogen that you

breathe in and the carbon in the tip of

your pencil however you may not

understand this group right here the

metalloids now metalloids are what is

know what are known as

semiconductors meaning

they have conduct tivity that's

between uh the conductivity of metals

which is very good and the conductivity

of non-metals which is very poor and

continuing with the theme of diversity

in the P block uh it contains in group

17 a group that are known as the

halogens and the halogens are the most

reactive

non-metals because if we follow our

group

rule 177 minus 10 we can see that they

have seven electrons in their outer

shell and this is one short of the octet

rule which is what the noble gases next

to them have which makes them extremely

stable now this closeness to stability

makes them extremely susceptible to

chemical reactions in order to obtain

this uh eight electron OCT octet which

is why the halogens are so reactive and

lastly we'll just briefly cover the F

block which are the lanthanides and

actinides now these are stuck sort of

off the bottom of the table in order to

save space and make sure it wasn't you

know massive side to side and the

lanthanides are between the lanthanides

and actinides both start between groups

three and four so right about

here and they are used to fill up the

F orbital which can hold which has seven

sub orbitals each holding two electrons

each so there are

14 in total ways of arranging and

therefore 14 elements in the sixth and

seventh periods within the F

block now the lanthanides and actinides

are very similar to each other so they

were very uh tedious to sort out and

then the actinides which are the bottom

row right here are all Radioactive and

then all of them after element 993

neptunium were all made in a lab

somewhere meaning they're all synthetic

elements so they're not naturally

occurring in nature people had to use

big particle accelerators and

bombard uh other elements with nuclei in

order to form them which is something

we'll study

later