GCSE Chemistry - Electron Arrangement #8
Summary
TLDRThis educational video explores electron arrangement in atoms, highlighting the importance of a full outer shell for stability. It demonstrates the electron configuration of sodium and explains how atoms like it tend to react to achieve stability. The video also covers noble gases, which are stable due to full outer shells, and provides examples of how to determine electron structures for elements like argon and calcium. It concludes with the case of fluorine, which gains an electron to become a fluoride ion, emphasizing the concept of ions and their charges.
Takeaways
- π¬ Atoms strive for a stable electron configuration, typically seeking a full outer shell.
- π Sodium, with an atomic number of 11, has an electron arrangement that leaves its outer shell with only one electron, making it unstable.
- π The first electron shell holds up to two electrons, while the second and third can hold up to eight each.
- π Electrons are added to shells in a specific order, starting with single electrons in corners before filling in pairs.
- π‘ Noble gases, like neon, have full outer shells and are chemically stable due to this configuration.
- π For exam preparation, knowing the electron arrangement of the first 20 elements in the periodic table is crucial.
- π Argon, with an atomic number of 18, has a full outer shell with its electron configuration written as 2, 8, 8.
- π Electron configurations can be represented numerically, showing the count of electrons in each shell.
- β‘ Calcium, with 20 electrons, has an unstable outer shell with only two electrons out of eight possible, leading to a +2 charge as a calcium ion.
- π Ions are represented with square brackets and the overall charge indicated in the top right corner.
- πΏ Fluorine, needing one more electron for a full outer shell, gains an electron to become a fluoride ion with a -1 charge.
Q & A
Why do atoms need a full outer shell of electrons to be stable?
-Atoms need a full outer shell of electrons to be stable because a complete outer shell means they have reached a stable electron configuration, typically resembling the noble gases, which are chemically inert due to their full valence electron shells.
What is the atomic number of sodium, and how does this relate to its electron configuration?
-The atomic number of sodium is 11, which means it has 11 protons and also 11 electrons. These electrons are arranged in shells around the nucleus, with the first shell holding 2 electrons and the second shell holding up to 8, leaving the third shell with 1 electron, making the outer shell incomplete.
How does the electron arrangement in an atom influence its chemical reactivity?
-The electron arrangement, specifically the completeness of the outer shell, influences an atom's chemical reactivity. Atoms with incomplete outer shells tend to react with other atoms to gain, lose, or share electrons to achieve a stable electron configuration.
What is the maximum number of electrons that the first and second shells can hold?
-The first shell can hold a maximum of 2 electrons, while the second shell can hold up to 8 electrons.
Why are noble gases chemically inert?
-Noble gases are chemically inert because they have completely full outer electron shells, which means they are already in a stable state and do not need to gain or lose electrons to achieve stability.
How many electrons does an argon atom have, and what is its electron arrangement?
-An argon atom has 18 electrons due to its atomic number. Its electron arrangement is 2 electrons in the first shell, 8 in the second, and 8 in the third shell, which can be represented as 2, 8, 8.
What is the electron arrangement for calcium, and why is it not stable?
-Calcium has an atomic number of 20, so it has 20 electrons arranged as 2 in the first shell, 8 in the second, 8 in the third, and 2 in the fourth shell. It is not stable because its outermost shell does not have a full complement of 8 electrons.
What happens when a calcium atom loses its two outermost electrons?
-When a calcium atom loses its two outermost electrons, it forms a calcium ion with a 2+ positive charge. The outermost shell then becomes the third shell, which is now full, making the ion stable.
What is the atomic number of fluorine, and what is its electron arrangement?
-Fluorine has an atomic number of 9, indicating it has 9 electrons. Its electron arrangement is 2 electrons in the first shell and 7 in the second shell, represented as 2, 7.
Why does a fluorine atom need to gain an electron to be stable?
-A fluorine atom needs to gain an electron to be stable because it has 7 electrons in its second shell, which is one electron short of the stable configuration of 8 electrons in the outer shell.
What is the resulting charge of a fluorine atom after it gains an electron?
-After gaining an electron, a fluorine atom becomes a fluoride ion with an overall charge of -1.
Outlines
π¬ Electron Arrangement and Atomic Stability
This paragraph delves into the electron configuration in atoms, emphasizing the importance of a full outer electron shell for atomic stability. It uses the example of a fluorine atom to illustrate the concept of incomplete outer shells and the subsequent need for atoms to react with others to achieve stability. The paragraph introduces the electron arrangement of sodium, explaining its atomic number and the shell structure, including the specific electron placement within each shell. It highlights the instability of sodium due to its incomplete outer shell and contrasts this with noble gases, which have full outer shells and are chemically inert. The video script also covers how to determine the electron structure of argon and calcium, explaining the process of drawing electron shells and the significance of a full outer shell for stability, leading to the formation of ions when atoms lose or gain electrons to achieve this state.
π Understanding Ions and Electron Configurations
The second paragraph continues the discussion on atomic stability by focusing on ions, specifically using calcium and fluorine as examples. It explains how calcium, with 20 electrons, forms a calcium ion by losing two electrons to achieve a stable electron configuration, resulting in a positively charged ion. The paragraph details the notation for ions, including the use of square brackets and the indication of the overall charge. It also contrasts this with fluorine, which gains an electron to complete its outer shell, becoming a negatively charged fluoride ion. The summary concludes with the electron configurations for both calcium and fluorine in their ionic forms, highlighting the changes in electron count and charge that result from the atoms' pursuit of a stable electron configuration.
Mindmap
Keywords
π‘Electron arrangement
π‘Atomic number
π‘Electron shell
π‘Stability
π‘Noble gases
π‘Electron configuration
π‘Ion
π‘Charge
π‘Periodic table
π‘Chemical reaction
π‘Electron capacity
Highlights
Video explores electron arrangement in atoms and its importance for atomic stability.
Atoms with incomplete outer shells, like fluorine, tend to react to achieve stability.
Sodium's electron arrangement is demonstrated with its atomic number of 11.
Electron shells fill in a specific order, starting with the lowest energy level closest to the nucleus.
The first electron shell can hold a maximum of two electrons.
The second shell can hold up to eight electrons, following a specific arrangement pattern.
Sodium's outer shell has only one electron, indicating instability and the need to react.
Atoms generally want to form molecules or compounds to achieve a full outer shell.
Noble gases, like neon, have full outer shells and are chemically stable due to this.
Argon's electron structure is explained with its atomic number of 18.
Electron arrangements can be represented numerically, as shown with argon's 2,8,8 structure.
Calcium, with an atomic number of 20, has an unstable electron arrangement.
Calcium atoms can become stable by losing two electrons, forming a calcium ion.
Ions are represented with square brackets and the overall charge indicated.
Fluorine, with an atomic number of 9, needs to gain an electron to achieve a full outer shell.
Fluorine forms a fluoride ion with a charge of minus one when it gains an electron.
The video concludes with a teaser for the next topic: balancing chemical equations.
Transcripts
in today's video we're going to take a
look at the arrangement of electrons in
atoms
and see how most atoms like the fluorine
that we've shown here have an incomplete
outer shell of electrons
this is a really key point in chemistry
because in order for atoms to be stable
they need to have a full outer shell
and if they don't then they'll have to
react with another atom they gain or
lose the electrons that they need
let's start by drawing the electron
arrangement of sodium
the fact that it has an atomic number of
11 tells us that there's 11 protons
but also that it has 11 electrons
these electrons are going to be arranged
in shells around the nucleus
which we draw as rings like this
and the first one to fill is the one
closest to the nucleus
as this one will have the lowest energy
level
this first shell can only hold two
electrons
the second shell though can hold up to
eight
and the order in which you add them can
sometimes be important
the best way to do it is to put a single
electron in the top
right bottom and left positions
before you go around again to put a
second electron in each position
this might seem a bit weird or
unnecessary but really you're just
adding them in clockwise until you've
either filled the shell or run out of
electrons
as we still have one electron left we
put it in the third shell
and just like the second shell the third
one can hold a maximum of eight
electrons
in order for atoms to be stable their
outermost shell meaning the one furthest
from the nucleus needs to be completely
full
you can see here that our sodium atom
only has one electron in its outer shell
rather than eight
so we would say that it's unstable
and all we mean by that is that it wants
to react with another atom so that it
can have a full outer shell
now most single atoms are like the
sodium that we just saw
if they weren't bonded to anything then
they would have incomplete outer shells
and so to fix this most atoms want to
react to form molecules or compounds
however there are some exceptions to
this
the noble gases in group zero of the
periodic table
all have completely full outer shells
as we can see with neon
and because of this they don't want to
lose or gain any electrons
and so they don't really react with
anything
when it comes to exams you could be
asked to work out the electron
arrangement of any of the first 20
elements in the periodic table
for example they could ask
what is the electron structure of argon
for this we first need to find argon on
the periodic table
and we can see that argon has an atomic
number of 18.
so we must also have 18 electrons
then after drawing a quick nucleus we
can start to draw the shells and
electrons
the first shell will have two electrons
the second shell will have eight and the
third shell will also have eight
because two plus eight plus eight gives
us eighteen
we can also show this electron structure
with numbers though rather than drawing
out all of these shells
and to do that we would just do two
comma eight comma eight
to show there's two electrons in the
first shell
eight in the second and eight in the
third
another thing to point out is that when
you come to draw these diagrams for
yourself you have to draw the electrons
either as crosses like this
or as dots like this one
what if we were asked to do the same for
calcium
well calcium has an atomic number of 20
so it must have 20 electrons
which means working out from our nucleus
we have two in the first shell
eight in the second
eight in the third
and two in the fourth
and if we were to write this structure
it would just be two
eight eight two
as we can see from this diagram calcium
atoms aren't stable
because they don't have a full outer
shell
they only have two out of eight possible
electrons in their fourth shell
what would help is if these two outer
electrons were somehow removed
this would mean that the outermost shell
which is now the third shell
would be full and so the calcium is
stable
however even though our calcium atom
still has 20 positive protons
it now has only 18 negative electrons
because remember it just lost two of
them
so overall it's gonna have a two plus
positive charge
and so we call it a calcium ion rather
than a calcium atom
with ions we always draw big square
brackets around them
and write the overall charge in the top
right corner
because our calcium atom lost two
electrons drew right to the electron
structure it would now just be two eight
eight
as a last example let's look at fluorine
its atomic number is nine so there are
nine protons and nine electrons
meaning we'd have two electrons in the
first shell and seven in the second
which we'd write as two comma seven
so here we'd have the opposite problem
to what we had with calcium
in order to be stable and have a full
outer shell fluorine needs to gain one
more electron
which you would have to get from another
atom
giving it an overall charge of minus one
and making it a one minus fluoride ion
and we could write this electron
structure as 2 8.
anyway that's it for this video if you
enjoyed it then please do give us a like
and we'll see you next time when we take
a look at how to balance chemical
equations
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