Chemistry Lecture 1 - Atoms
Summary
TLDRThis 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
🔬 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.
🌐 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.
🔍 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.
⚛️ 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.
Mindmap
Keywords
💡Subatomic particles
💡Protons
💡Neutrons
💡Electrons
💡Atomic number
💡Mass number
💡Periodic table
💡Chemical symbols
💡Electron shells
💡Isotopes
💡Hydrogen ion
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
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