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3 years ago

A student says: Potassium (K) always has 20 protons. Explain why the student is incorrect.

Chemistry

1 answer:

Katen [24]3 years ago

5 0

Explanation:

Potassium/Atomic number

This tells you that potassium has 19 protons and - since the number of protons is the same as the number of electrons- also 19 electrons. To find out the number of neutrons you have to look at the atomic mass or weight of the element. This can also be found in the periodic table.

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3 years ago

Read 2 more answers

Write the symbol for each of the following ions:

kap26 [50]

Answer:

a) $_{31}^{71}\textrm {P^{3+}}$

b) $_{35}^{80}\textrm {Br^{-}}$

c) $_{90}^{232}\textrm {Th^{4+}}$

d) $_{38}^{87}\textrm {Sr^{2+}}$

Explanation:

For neutral atoms:

Atomic Number (Z)= number of protons = number of electrons

Mass number (A) = number of protons + number of neutrons

For ions with positive net charge:

Number of protons = Z + net charge

For ions with negative net charge:

Number of protons= Z - net charge

a) A = 71, Charge = +3

Number of electrons = 28

Number of protons = 28 +3 =31

$_{31}^{71}\textrm {P^{3+}}$

b) A = 35, Z = 45+35=80, Charge = -1

Number of protons =35

Number of neutrons = 45

Number of electrons = 36

Charge = Number of protons- Number of electrons =35-36 = -1

$_{35}^{80}\textrm {Br^{-}}$

c) Charge = +4

Number of electrons = 86

Number of protons = Z = 86+4 = 90

mass number = A = 90+142 = 232

$_{90}^{232}\textrm {Th^{4+}}$

d) Charge = +2

Atomic number = Number of protons = Z = 38

mass number = A = 87

$_{38}^{87}\textrm {Sr^{2+}}$

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3 years ago