Download How Atoms Bond: Ionic Bonds

How Atoms Bond: Ionic Bonds
https://archives.nbclearn.com/portal/site/k-12/browse/?cuecard=56354
General Information
Source:
Creator:
NBC Learn
Beth Nissen
Resource Type:
Copyright:
Event Date:
Air/Publish Date:
01/10/2012
01/10/2012
Copyright Date:
Clip Length
Video Science Explainer
NBCUniversal Media,
LLC.
N/A
00:06:28
Description
This NBC Learn video uses common table salt to explain and illustrate what happens between the
electrons and protons in atoms of the element sodium and atoms and the element chlorine to make crystals
of sodium chloride.
Keywords
Atom, Atoms, Bond, Bonds, Bonding, Ionic, Ions, Molecules, Particles, Electrons, Share, Transfer, Shell,
Shells, Outermost, Valence, Protons, Neutrons, Nucleus, Nuclei, Matter, Compounds, Element, Atomic
Number, Charge, Charged, Positive, Positively, Negative, Negatively, Neutral, Sodium, Chlorine,
Sodium Chloride, Crystal, Rule of 8, Octet Rule, Covalent, Hydrogen, Chemical Bonds, Chemistry Now
Citation
© 2008-2015 NBCUniversal Media, LLC. All Rights Reserved.
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MLA
"How Atoms Bond: Ionic Bonds." Beth Nissen, correspondent. NBC Learn. NBCUniversal Media. 10
Jan. 2012. NBC Learn. Web. 21 November 2015
APA
Nissen, B. (Reporter). 2012, January 10. How Atoms Bond: Ionic Bonds. [Television series episode].
NBC Learn. Retrieved from https://archives.nbclearn.com/portal/site/k-12/browse/?cuecard=56354
CHICAGO MANUAL OF STYLE
"How Atoms Bond: Ionic Bonds" NBC Learn, New York, NY: NBC Universal, 01/10/2012. Accessed
Sat Nov 21 2015 from NBC Learn: https://archives.nbclearn.com/portal/site/k-12/browse/?cuecard=56354
Transcript
How Atoms Bond: Ionic Bonds
BETH NISSEN, reporting:
Over the course of time, a few students may have asked, “Why does chemistry matter?”
And the answer, of course, is matter: all matter in the universe.
Anything that can be physically touched, anything living, is made up of atoms – which join together to
form molecules, which join together into compounds, until you’ve got, say, a spoon, or a tree, or a
hedgehog.
How does this happen – how do atoms join together, or bond, to form molecules?
Let’s take a close look –
really
close: atoms aren’t even big enough to be microscopic.
As eensy as atoms are, they’re made up of even smaller particles: neutrons, protons, and electrons. A
diagram of an atom looks like this: “shells” surrounding a center, or nucleus. Inside the nucleus are all of
that atom’s protons (and neutrons). Moving all around the shells are that atom’s electrons.
Let’s focus on protons first. The protons in the atom’s nucleus stay there – an atom of a particular element
will always have, and keep, the same number of protons.
That number of protons is so permanent (memory trick: ‘proton’ and ‘permanent’ both start with ‘p’) that
it’s part of the information in the Periodic Table: that number, usually at the top of each square, is the
atomic number – the number of protons in the nucleus of an atom of this element.
Look at sodium (abbreviated Na). A sodium atom has 11 protons in its nucleus. The atomic number also
tells you how many electrons there are: individual atoms of every element have the
same number of protons and electrons
. So a sodium atom has 11 protons, 11 electrons.
Pop Quiz #1: How many electrons are there in an atom of chlorine (abbreviated Cl)?
Answer: 17 – same as the number of protons.
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While the number of protons and electrons in each atom is the same, protons and electrons are very
different…with different ‘electric’ charges. Protons have a positive ‘electric’ charge. (Add to the earlier
memory trick: ‘p’ for ‘proton,’ ‘permanent’ and ‘positive’ and ‘plus.’).
Electrons (which, by the way, are much smaller than protons) are the opposite: they have a
negative
charge.
And atoms themselves? Heads up – this next part contains information that might prove useful in a later
quiz: Because atoms
have equal numbers of positive protons and negative electrons
, the electric charges cancel each other out. Net charge: zero.
OK, now back to electrons. While the positive protons are permanently in the atom’s nucleus, the negative
electrons in an atom are not: electrons move around in the shells. And -- this is key – unlike protons, the
number of electrons in an atom can change…and do, when and if atoms bond.
To explain this step by step, let’s use a simple everyday example: how atoms of the element Na,
sodium…and atoms of Cl, chlorine…form a bond – an ionic bond – to make NaCl, the abbreviation for
sodium chloride, more commonly known as salt.
Atoms bond by ‘swapping’ or transferring electrons from their outermost shells, called valence shells. It’s
a little like an atomic version of the card game Go Fish: each one wants to let go of or pick up enough
electrons so it ends up with a particular number of electrons in its outermost shell – very often a total of 8.
This is so common, it’s called the Octet Rule, or Rule of 8.
Look how many electrons Chlorine has in its outer shell: 7. Sodium? One. Sodium gives up one electron,
which chlorine picks up. That gives chlorine the ‘magic 8’ electrons in its valence shell.
Giving up that one lone electron empties sodium’s outermost shell – think of it as a “Go Fish” player with
no cards to trade, who has to drop out. The 2nd shell now becomes the outermost ‘valence’ shell. It still
has electrons to ‘trade’ – actually, 8 of them. So sodium, too, now has its ‘magic 8.’
Pop Quiz #2 – NOW how many electrons are in each sodium atom? (To remind you, this is sodium’s
atomic number.)
Answer: 10 – because it gave one of its 11 electrons to chlorine.
The positive protons in the atom now ‘outnumber’ the negative electrons, 11 to 10. So sodium is no longer
neutral – it now has a positive charge, indicated with a ‘plus’ sign, and is a sodium ion (that’s the term for
an atom with an unequal number of protons and electrons).
Pop Quiz #3 – How many electrons are in chlorine now?
Answer: 18 – which means the chlorine atom is now an ion, too: 18 negative electrons outnumber 17
positive protons, which gives chlorine a negative charge, and changes its abbreviation to Cl-minus. (And
also changes ‘chlorine’ to ‘chloride.’)
You probably know: opposites attract. Positive sodium and negative chloride ions are strongly attracted to
each other – and that attraction is what bonds Na+ and Cl- ions together form NaCl: sodium chloride.
Most chemical bonds are ionic, like the ones that forms salt, or covalent – that’s where atoms don’t give
up and pick up electrons, but share them to fill their outer shells…H
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2
O is a good example of that.
There’s much more to know about all this – but now you have at least an “elementary” understanding of
how atoms bond.
(And the smart answer to the question: what’s the matter?)
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