Chemistry Lecture 1 - Atoms

Summary

This educational script delves into the fundamentals of atomic structure, focusing on subatomic particles like protons, neutrons, and electrons. It explains the significance of atomic number, which corresponds to the proton count in an element's nucleus, and mass number, the sum of protons and neutrons. The script simplifies complex concepts like electron shells and their capacities, using carbon and nitrogen as examples. It also introduces isotopes, variations of elements with different neutron counts but the same atomic number, and concludes with a discussion on hydrogen ions, emphasizing their role in chemistry and biology.

Takeaways

• 🔬 Atoms are composed of subatomic particles: protons and neutrons in the nucleus, and electrons orbiting the nucleus.
• ⚛️ Protons carry a positive charge, electrons carry a negative charge, and neutrons are neutral.
• 🔢 The atomic number of an element is the count of protons in the nucleus, which defines the element's identity.
• 📊 The mass number of an element is the sum of protons and neutrons in the nucleus, influencing the element's weight.
• 🧬 Electrons are organized in shells around the nucleus, with the first shell holding up to two electrons and subsequent shells holding up to eight.
• 🌐 The periodic table lists elements by atomic number, each with a unique mass number and chemical symbol.
• 💡 Memorizing the chemical symbols for 12 key elements critical to human life is essential, including O (oxygen), C (carbon), H (hydrogen), N (nitrogen), P (phosphorus), S (sulfur), Ca (calcium), Cl (chlorine), Mg (magnesium), K (potassium), Na (sodium), and Fe (iron).
• 🔋 Electron configurations, particularly the number of vacancies in the outer shell, are crucial for understanding chemical bonding and reactivity.
• 📈 Isotopes are variants of an element with the same atomic number but different mass numbers due to varying neutron counts.
• ⚡ A hydrogen ion, formed when a hydrogen atom loses its electron, is essentially a proton with a positive charge, denoted as H+.

Q & A

What are the subatomic particles that make up an atom?

An atom is made up of subatomic particles which include protons and neutrons found in the nucleus, and electrons that orbit around the nucleus.

What is the charge of protons, electrons, and neutrons?

Protons are positively charged, electrons are negatively charged, and neutrons are neutral, meaning they do not carry a charge.

What is the atomic number of an element, and what does it represent?

The atomic number of an element is the number of protons found in the nucleus of its atoms. It defines the identity of the element.

How is the mass number of an element determined?

The mass number of an element is determined by adding the number of protons and neutrons together.

Why do electrons not weigh much compared to protons and neutrons?

Electrons do weigh something, but their mass is significantly less compared to protons and neutrons, which is why they have a smaller impact on the overall mass of an atom.

What is the significance of the periodic table in relation to elements?

The periodic table is a tabular arrangement of elements based on their atomic number, properties, and chemical behavior. It is a fundamental tool in chemistry and science, representing each element with its unique atomic number and mass number.

How many chemical symbols for elements are critical to human life according to the script?

According to the script, there are 12 chemical symbols for elements that are critical to human life.

What is the chemical symbol for oxygen, and how is it derived?

The chemical symbol for oxygen is 'O', which is derived from the first letter of the word 'oxygen'.

How many electrons can the first electron shell hold, and what is the general capacity for subsequent shells?

The first electron shell can hold two electrons, and subsequent shells can generally hold up to eight electrons each.

What is the difference between an atom and an ion?

An atom is a neutral entity with an equal number of protons and electrons, while an ion is an atom or molecule that has lost or gained electrons, resulting in a net charge.

What is a hydrogen ion, and how is it represented?

A hydrogen ion is a hydrogen atom that has lost its electron and is left with just a proton. It is represented as 'H+'.

What are isotopes, and how do they differ from one another?

Isotopes are atoms of the same element with the same atomic number but different mass numbers due to a different number of neutrons.

Outlines

00:00

🔬 Fundamentals of Atoms and Subatomic Particles

This paragraph introduces the basic structure of atoms, emphasizing the roles of subatomic particles such as protons, neutrons, and electrons. Protons and neutrons reside in the nucleus, with protons carrying a positive charge and neutrons being neutral. Electrons orbit the nucleus and have a negative charge. The atomic number, which is the count of protons in the nucleus, is highlighted as a key identifier of an element. For instance, carbon's atomic number is six, indicating six protons in its nucleus. The mass number is also introduced, defined as the sum of protons and neutrons, which correlates to the element's weight. The paragraph concludes with a practical example, illustrating how to calculate the number of neutrons in an element given its atomic and mass numbers.

05:00

🌐 The Periodic Table and Chemical Symbols

The paragraph delves into the significance of the periodic table, portraying it as a fundamental tool in science that lists elements with unique atomic and mass numbers. It then transitions into a discussion about chemical symbols, which are abbreviations of element names. The speaker encourages students to familiarize themselves with 12 essential chemical symbols for human life, starting with the simpler ones like Oxygen (O), Carbon (C), Hydrogen (H), Nitrogen (N), Phosphorus (P), and Sulfur (S). The paragraph also touches on the unique symbols for Calcium (Ca), Chlorine (Cl), Magnesium (Mg), and the more complex ones derived from Greek words for Potassium (K), Sodium (Na), and Iron (Fe). The speaker uses humor to engage the audience and emphasizes the importance of knowing these symbols for exams.

10:03

🔍 Electron Configuration and Isotopes

This section explores the concept of electron shells and their capacity to hold a specific number of electrons, with the first shell holding two and subsequent shells holding up to eight. The speaker uses examples of nitrogen, oxygen, and magnesium to demonstrate how electrons fill these shells and how vacancies in the outer shell are calculated. The concept of isotopes is introduced, explaining that isotopes are versions of the same element with different mass numbers due to varying neutron counts. The paragraph clarifies that isotopes are not inherently radioactive, challenging a common misconception. The distinction between elements and their isotopes is made clear, with the most common version being referred to as the element itself.

15:08

⚛️ Hydrogen Ion Formation and Its Significance

The final paragraph focuses on hydrogen, the element with an atomic number of one, which typically has a single proton and no neutrons in its most common form. It discusses how hydrogen atoms, with one electron and one vacancy in their outer shell, tend to lose this electron to achieve a stable configuration. This loss results in the hydrogen atom becoming a positively charged ion, specifically a proton, which is denoted as H+. The paragraph simplifies the concept by stating that a hydrogen ion is essentially a proton, reinforcing the idea that ions result from an imbalance between the number of protons and electrons in an atom or molecule.

Keywords

💡Subatomic particles

Subatomic particles are fundamental units that make up atoms. In the context of the video, these include protons, neutrons, and electrons. Protons and neutrons reside in the nucleus, while electrons orbit around it. The video emphasizes that understanding these particles is crucial for grasping atomic structure, which is foundational for the study of chemistry and biology.

💡Protons

Protons are subatomic particles with a positive electric charge. They are located in the nucleus of an atom. The video explains that the number of protons in an atom's nucleus defines the atomic number of an element. For instance, carbon has six protons, hence its atomic number is six.

💡Neutrons

Neutrons are subatomic particles found in the nucleus of an atom that have no electric charge. They contribute to the mass of an atom but not to its charge. The video clarifies that neutrons, along with protons, determine the mass number of an element, which is the sum of protons and neutrons.

💡Electrons

Electrons are negatively charged subatomic particles that orbit the nucleus of an atom. They are crucial for understanding chemical reactions and the formation of molecules. The video simplifies the concept by likening electrons to the moon orbiting the earth, emphasizing their structured arrangement in electron shells.

💡Atomic number

The atomic number of an element is the count of protons in the nucleus of its atoms. It is a key identifier of an element, as explained in the video using carbon as an example, which has an atomic number of six, meaning it has six protons.

💡Mass number

The mass number of an atom is the sum of the number of protons and neutrons. It is a measure of the atom's mass. The video uses the example of an element with an atomic number of nine and a mass number of 21 to illustrate that the number of neutrons can be calculated by subtracting the atomic number from the mass number.

💡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 fundamental tool in chemistry and biology, as it displays the unique mass numbers and other characteristics of elements. The video mentions that each element on the periodic table has its own unique mass number.

💡Chemical symbols

Chemical symbols are abbreviations used to represent elements, typically consisting of one or two letters. The video emphasizes the importance of knowing the chemical symbols for 12 elements critical to human life, such as Oxygen (O), Carbon (C), and Hydrogen (H). These symbols are used to write chemical formulas and understand molecular structures.

💡Electron shells

Electron shells are regions around the nucleus where electrons are located. The video explains that electrons are not distributed randomly but are arranged in shells, with the first shell holding up to two electrons and subsequent shells holding up to eight. This structured arrangement influences how atoms bond with each other.

💡Isotopes

Isotopes are atoms of the same element (having the same number of protons) but differing in the number of neutrons. The video clarifies that isotopes have the same atomic number but different mass numbers. It also dispels the common misconception that all isotopes are radioactive, noting that while some are, many are not.

💡Hydrogen ion

A hydrogen ion, as discussed in the video, is a hydrogen atom that has lost its electron, resulting in a positively charged ion. This ion is essentially a proton, which is the nucleus of a hydrogen atom. The video uses the hydrogen ion to illustrate how atoms can become ions through the loss or gain of electrons.

Highlights

Atoms are composed of subatomic particles: protons, neutrons, and electrons.

Protons are positively charged, electrons are negatively charged, and neutrons are neutral.

The atomic number of an element is the number of protons in its nucleus.

The mass number of an element is the sum of protons and neutrons.

Electrons have a minimal effect on an atom's mass compared to protons and neutrons.

The periodic table organizes elements by atomic number and provides unique mass numbers for each.

There are 12 critical chemical symbols for human life that students should memorize.

The chemical symbols for oxygen, carbon, hydrogen, nitrogen, phosphorus, and sulfur are their first letters.

Calcium, chlorine, and magnesium have chemical symbols derived from their first letters.

Potassium, sodium, and iron have chemical symbols based on their Greek names: K, Na, and Fe.

Electrons are organized into shells with the first shell holding up to two electrons and subsequent shells holding up to eight.

The number of vacancies in an atom's outer shell can be determined by its atomic number.

Isotopes are atoms of the same element with different numbers of neutrons, resulting in different mass numbers.

Not all isotopes are radioactive; isotopes can be stable or unstable depending on their neutron count.

A hydrogen ion is a proton with a positive charge, resulting from the loss of its single electron.

Transcripts

all right so we left off about here and we are talking about atoms and now

that we know a little bit about atoms we know that they are made out of

subatomic particles

and those subatomic particles that you need to know are protons and neutrons

which are found in the nucleus and electrons that go around on the

outside and we've learned that protons are

positively charged electrons are negatively charged and

neutrons they're neutral they don't they don't have a charge um

so we're learning some definitions and one of the definitions that you need to

know is atomic number the atomic number

of any given element is going to be the number of protons

that are found in the nucleus of their atoms so for example the atomic number

for carbon is six that means any atom of carbon

has got six protons in the nucleus if i told you that in my hand i had some

carbon but it had seven protons in the nucleus

you would have to say well then you don't have carbon okay

because carbon's got an atomic number of six which means

all of its atoms have got six protons in the nucleus the atomic number

now the mass number is going to be the number of protons plus the number of

neutrons when it comes to how much something

weighs the mass of it for a certain number of

its atoms when it comes to that the um

you add up the number of protons and the number of neutrons

do the electrons weigh something uh they weigh

something but they don't weigh very much so let's go here i'm going to draw

something come back all right so

if i were to ask if i were to tell you that i have got

in my hand an element and its atomic number is nine and its

mass number is 21. tell me how many neutrons does it have

so you would say the atomic number is nine

oops and do that right if the atomic number is nine

and

the atomic number is nine then that means it has nine protons

that's just not working at all

it's got nine protons okay and you and i told you that its mass number was

21 so that's its mass number okay

so how many um neutrons does it have it has 12 neutrons

why because if you add up the protons and the neutrons

you get the mass number all righty so when we're talking about

elements we're talking about

the periodic table the periodic table of elements is sort of like

you know the thing you put on a t-shirt when you want people to know that your

movie character is a nerd it's kind of the symbol for

science and elements

are individually listed here each element

has got a unique mass number every element has got its own mass

number so here you can see carbon has got an

atomic number six so it has six protons a mass number of 12

so most of the atoms of carbon have got six neutrons as well

so these are all the elements now from biology

point of view we only care about some of these

which is why my mastery of chemistry is not as good as yours

probably will be very soon or might already be

but i do want you to know the 12 chemical symbols for the elements that

are critical to human life you know they call them chemical symbols

like like it's going to be an apple or something like that

but they're not icons they're really just the abbreviations

and you need to know 12 of them let's start with the easy ones by the way

i told you in the introductory part of the class that

it is a good strategy while you're watching these lecture videos

to have already printed up the study guide

so you can be answering study guide questions

as you're listening to lecture here's a place where this is actually

written in the study guide so you could fill it in

so these guys are the easy ones oxygen carbon hydrogen

most of the weight of every living thing whether it's a tree or a blue whale or

you and it is made out of oxygen carbon and

hydrogen um but also nitrogen phosphorus and

sulfur these guys what is their chemical symbol

it is the first letter of the word so for oxygen

it's o for carbon it's c for hydrogen it's the letter h hydrogen for nitrogen

it's the letter n there you are over there

for phosphorus it's the letter p for sulfur is the letter

s right so we got those out of the way that's

five right there now these three these are pretty easy

um the letter c got used as the symbol for carbon so what are we going to do

with calcium and chlorine well for calcium we made it ca

and for chlorine we made it cl cl magnesium magnesium is

mg right those are pretty easy then we've got three of them that are

hard sorry they're just hard uh and the

reason is that um their chemical symbol was

assigned based on their uh their the Greek word

for the element so for potassium the chemicals chemical symbol is the

letter k uh for sodium the chemical symbol is

capital N lowercase a and for iron the chemical symbol is

capital F lowercase e alrighty so make sure you know that because on

the exam there's going to be a question like the

chemical symbols for calcium and sodium are and you need to know

Ca and Na right good oh yeah nerd humor i hear oxygen and

magnesium are dating and i was like omg because the chemical symbol for oxygen

is o and the chemical symbol for magnesium is

mg yeah i got lots of these

so we've talked about quite a bit let's talk about

electrons now the reason that we're talking about atoms at all

is so i can talk to you about electrons because understanding electrons will

allow us to understand how molecules get put together

now electrons are kind of orbiting around the nucleus are they

actually orbiting the way the moon orbits the earth? no, not exactly

but it's okay to think of it that way as long as you're in biology.

i'm not even going to explain the way it really works okay.

now even though the electrons are orbiting the nucleus they

are not doing it randomly. we don't just have a whole bunch of electrons just (woowoowoo)

they are in what are called electron shells.

the first electron shell is the shell that is

closest to the nucleus and it is only capable of holding

two electrons. so once uh there is an atom that let's imagine

the atom has got three electrons in it. well, the first two

will go into the first electron shell but that third electron needs to go in

the next shell outward all right the first

electron shell can hold two and then it's filled the next one

and the third one they can each hold eight

right the first electron shell can hold two the outermost electron shell can

hold eight now if you were talking about elements

that are bigger than the ones we're gonna be talking about

things are different but i'm just gonna set that aside okay?

remember two for the first one; eight for the other ones.

so one of the questions that you're going to bump into on exam one

is going to be something like "i have got an

atom it has got an atomic number of seven

how many electrons are in its outer shell?" how many vacancies are in its

outer shell? let's do that. okay here's nitrogen it's

got an atomic number of seven. if it doesn't have any charge no net

charge then it'll have seven protons and seven

electrons. great. seven electrons it is going to put two

electrons in the first electron shell. great.

now it's got five left over and so it'll have

five in the outer electron shell because the outer electron shell

can hold eight but right now it's got five in it. that means the outer electron

shell has got three vacancies. yes, this is a very

stupid game right now but actually it's gonna mean something

in another slide or two. okay so make sure that you can do that.

oxygen's got an atomic number of eight. when it has no charge how many electrons

does it have? an atomic number of eight means it's got

eight protons. if it has no net charge it has eight

electrons. the first two electrons go in the first

shell that leaves six more. so there are six electrons in the

outer electron shell and it could hold eight so that leaves

two vacancies. right let's go ahead and do it with

magnesium it's got an atomic number of 12.

how many protons does magnesium have dumb question 12. already now

i've written here that's got 12 neutrons. do you need to memorize that?

oh please don't! all right don't memorize any rules for it.

the only thing you need to know about neutrons is that they're neutral,

that they're calculated in the atomic mass or the

yeah the atomic mass you need to know that

right so how many electrons are in the outer electron shell well we've got 12

protons and it's got no charge so we're going to

put the first two in the first shell and then we've got 10 more to go so the

next shell we will put electrons 3 4 5 6

7 8 9 10 okay we still have two more to go so the

outer electron shell holds two so the louder electron shell has got

two electrons how many vacancies six vacancies

right so go ahead and practice those now what is the atomic number of this

element well it says right there's got 13

protons so the atomic number is

13. okay what's its mass number for the mass number we take the number

of protons and add the number of neutrons

so the mass number for this element is 25.

simple right now what did i do here you know i know i added all those words

but look it has got a different number of neutrons.

is it the same element as this one? yes because the atomic number the number

of protons dictates which element it is. i don't

know what this element is okay but that is going to be what dictates

what element it is. this one (boom) same number of protons

but different number of neutrons so it's the same element but it's different

somehow. how do we describe that? we would say

that this one with a mass number of 25 and this one with a mass number of 27

that these guys are the same element but they are different isotopes. okay?

here we go isotopes are atoms that have the same atomic number

(they're the same element) but they have different mass numbers

a different number of neutrons all right now when you think about isotopes you're

probably thinking oh that means they're radioactive. not

always. okay um yes being an isotope

can make an atom radioactive but not all isotopes are radioactive

and by the way by convention we generally refer to the most common

version of the element as like being the element and then

whatever is the less common thing we call (excuse me) the isotope

for example carbon-12 almost all the carbon that you bump into on a

day-to-day basis (and we're mostly made out of it almost all

of it) is carbon-12 so we have a tendency to

call that carbon and then uh

because it's got six protons and six neutrons and then

carbon 13 it's got six protons and seven neutrons

we call that an isotope but don't worry about the technicality. i'm

not going to quiz you on it. okay oh what do we need to know here

what is a hydrogen ion? all right. let's put together some of the stuff

we've been talking about, right? hydrogen has got an atomic number of one

and it generally has got a mass number of one

and that's because almost all the hydrogen around you

has got a single proton in the nucleus of its atoms

and no neutron. now, when hydrogen has no charge it has a single electron.

so technically an uncharged hydrogen atom

looks like this picture here one proton one

electron

now for reasons we're going to about to talk about at the beginning of the next

lecture atoms don't like this situation they

don't like having a vacancy in their outer electron

shell. hydrogen's got one electron and one

vacancy and it does not like that and it solves that problem in a couple

of ways. one way it solves the problem is by

giving away its electron. that's one way it solves

its problem. now, if hydrogen gives away its electron

two things happen; one thing is it becomes an

ion because i told you that whenever there

is not an equal number of protons and electrons

then that atom or molecule will have a charge. so technically it

will be an ion and it will have

a charge of plus one. also just have a look at this hydrogen atom.

if you took away an electron what do you have left?

you just have a proton. okay hydrogen's got an atomic number of one.

it's got one proton in its nucleus if it has no charge it'll have one

electron. what does a hydrogen atom look like when

it loses its electron? it is just going to be a naked proton.

okay so a hydrogen ion is sorry a hydrogen ion is a proton

and a hydrogen ion

a hydrogen ion is a proton

that's not working a hydrogen ion is a proton

and a hydrogen ion is also abbreviated H with a plus next to it

we'll we'll start off there in the next section