1) how many electrons are in each energy level of the following elements? a. he b. na c. na d. ne 2) how many valence electrons are percent in the following atoms? a. s b. mg c. be d. cl 3) which of the following elements are stable as atoms? a. he b. o c. cl d. ar if you are able to provide the work as to how you got the answers that would be greatly appreciated. : )

Answers:

Q1:

a. He: (2 electrons) 1s²

It has only 2 electrons and they are in the first level.

b. Na: (11 electrons) (2,8,1) 1s² 2s² 2p⁶ 3s¹

It has 2 electrons in the first level, 8 electrons in the second level, and 1 electron in the third level.

c. Na: is repeated like b

If it is Na⁺: (10 electrons) (2,8) 1s² 2s² 2p⁶

it will be like Ne and it has 2 electrons in the first level, and 8 electrons in the second level.

d. Ne: (10 electrons) (2,8) 1s² 2s² 2p⁶

it has 2 electrons in the first level, and 8 electrons in the second level.

Q2:

The valence electrons in the following atoms are:It can be known via electronic configuration, the valence electrons are the electrons found in the outermost shell:

a. S: (16 electron) (2,8,6) [Ne] 3s² 3p⁴

The valence electrons of S are 6 electrons.

b. Mg: (12 electron) (2,8,2) [Ne] 3s²

The valence electrons of Mg are 2 electrons.

c. Be: (4 electrons) (2,2) 1s² 2s²

The valence electrons of Be are 2 electrons.

d. Cl: (17 electrons) (2,8,7) [Ne] 3s² 3p⁵

The valence electrons of Cl are 7 electrons.

Q3:

a. He and d. Ar

Explanation:

He and Ar are the stable atoms because they are from noble elements.Noble elements are highly stable that it is completely filled with electrons in its outer shell applying octet rule.He (2 electrons) 1s², the first level is completely filled.Ar (18 electron) (2,8,8) 1s² 2s² 2p⁶ 3s² 3p⁶, the outer most shell (the third level) is completely filled with electrons (8 electrons)

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