Valence Electrons

Science 10

Valence Electrons

ELECTRONS SPIN around the nucleus in a region called SHELLSin any direction (upwards, downwards, sideways, etc.) as long as they stay in their shells.

Shells are areas that surround the nucleus of an atom, like layers around anonion.

Electrons “live” in these shells.

The shell is the distance from the nucleus that the electron spins.

Electrons in the first shell are always closer to the nucleus than the electrons inthe second shell.

A shell is sometimes called an orbital or energy level.

Each shell ONLY HOLDS a Certain number of ELECTRONS

Electron shells show the number of electrons in the shells of atoms. Each shell can accommodate a certain number of electrons but no more.

The first shell can only hold a maximum of 2 electrons.

The second shell can only hold a maximum of 8 electrons.

The third shell can only hold a maximum of 8 electrons.

You draw three shells and show the number of electrons in the first shell, the second shell and then the third shell.

The outer shell is called the valence shell. The electrons on it are called valence electrons.

The outer electrons determine the element's chemical properties.

Scientists use letters to name the orbitals around a nucleus. They use the letters "k,I,m,n,o,p, and q". The "k" shell is the one closest to the nucleus and "q" is the furthest away.

Not all shells hold the same number of electrons. For the first 18 elements, there are some rules. The k-shell only holds two electrons. The 1-shell only holds eight electrons. The m-shell only holds eight electrons (for the first 18 elements). The m-shell can actually hold up to 18 electrons as you move up the periodic table. You will learn more about this in Chemistry 11.

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In your own words, explain the pattern you can see above.

You can also use an electron dot diagram (also known as the Lewis diagram) to show an atom and its valence electrons. The electrons in the valence shell are shown as dots placed around the symbol.

You can place the dot anywhere (on top of the symbol, below the symbol, etc.), although you might find it easier to start with the first dot at the top of the symbol as you can see in the diagram below with H. Continue adding dots in a clockwise direction for each electron. When there is more than four dots (like the five) you start arranging the dots in pairs.

Fill in the missing electron dots in the Lewis electron diagrams below.

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H / He
•
Li / Be / B / F / Ne
Na / Mg / Al / Si / P / s / Cl / Ar
K / Ca

What pattern do you see happening in the diagram above?

Element Symbol / Group Number / Valence Electrons / Lewis Diagram / Bonding Electrons / Paired electrons
Mg
Al
P
S
Cl
Ar