5.2 Electron Configuration and the Periodic Table
Summary
TLDRThis 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
🔬 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.
🔋 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.
🌐 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.
Mindmap
Keywords
💡Electron Configuration
💡Periodic Table
💡Noble Gases
💡Octet Rule
💡Valence Electrons
💡Groups and Periods
💡Sublevels
💡S Block
💡D Block
💡P Block
💡F Block
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
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