Write complete symbols, including mass number and atomic number, for atoms with

Question

Write complete symbols, including mass number and atomic number, for atoms with the following characteristics.

Enter the number of electrons in each energy level (shell) for the following elements. If the energy level does not contain any electrons, enter a O (zero). It may help to refer to the periodic table. a) H n=1 n=2 n=3 n=4 b)N c)Mg d)K What is the neutral atom that has its first two energy levels filled, has 7 electrons in its third energy level, and has no other electrons? Enter the name of the element, not the abbreviation. ____________

Explanation / Answer

a)

H = has 1 electron, the eletronic configuration

1s1; then, n = 1; e = 1

b)

N = 7 electrons; the eletronic configuration

1s2 2s2 2p3

then,

n = 1; e = 2

n = 2; e = 4

c)

Mg = 12 electrons

electorn configuration

1s2 2s2 2p6 3s2

n = 1; e = 2

n = 2 ; 2+6 = 8

n = 3; e = 2

finally

d)

K

1s2 2s2 2p6 3s2 3p6 4s1

n = 1; e = 2

n = 2; e = 2+6 = 8

n = 3, e = 2+6 = 8

n = 4; e = 1

Quesiton 2.

neutral atom with first two energy levels, has 7 electrons in the 3rd level

and no other electrons...

1s2 and 2s2 2p6 istrue

3s2 3p5 = 7 electron

then

1s2 2s2 2p6 3s2 3p5

total e- = 2+2+6+2+5 = 17

this must be Chlorine, Cl

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