Answer
The symbol of an element X can be demonstrated as,
$_{Atomic number } ^{Mass number }X$
Atomic number = Number of protons(p)
Mass number = Number of protons(p) + Number of neutrons (n) = p+ n
If the number of electrons (e) = number of protons(p) , then the atom is neutral.
If the number of electrons (e)is less than the number of protons , then the atom have positive charge. The difference in number is the charge of the ion.
a)
The number of protons(p) = 94, hence atomic number is 94 and it denotes Plutonium(Pu).
Mass number = p + n = 94 + 150 = 244
p = e = 94, means atom is neutral.
Hence it’s symbol is,
$_{94} ^{244}Pu$
b)
The number of protons(p) = 79, hence atomic number is 79 and it denotes Gold(Au).
Mass number = p + n = 79 + 118 = 197
p > e, p-e = 3, means atom have 3+ charge .
Hence it’s symbol is,
$_{79} ^{197}Au^{3+}$
c)
The number of protons(p) = 34, hence atomic number is 34 and it denotes Selenium (Se).
Mass number = p + n = 34 + 45 = 79
p = e = 34, means atom is neutral.
Hence it’s symbol is,
$_{34} ^{79}Se$
d)
The number of protons(p) = 56 hence atomic number is 56 and it denotes Barium (Ba).
Mass number = p + n = 56 + 80 = 136
p = e = 56, means atom is neutral.
Hence it’s symbol is,
$_{56} ^{136}Ba$
Work Step by Step
The symbol of an element X can be demonstrated as,
$_{Atomic number } ^{Mass number }X$
Atomic number = Number of protons(p)
Mass number = Number of protons(p) + Number of neutrons (n) = p+ n
If the number of electrons (e) = number of protons(p) , then the atom is neutral.
If the number of electrons (e)is less than the number of protons , then the atom have positive charge. The difference in number is the charge of the ion.
a)
The number of protons(p) = 94, hence atomic number is 94 and it denotes Plutonium(Pu).
Mass number = p + n = 94 + 150 = 244
p = e = 94, means atom is neutral.
Hence it’s symbol is,
$_{94} ^{244}Pu$
b)
The number of protons(p) = 79, hence atomic number is 79 and it denotes Gold(Au).
Mass number = p + n = 79 + 118 = 197
p > e, p-e = 3, means atom have 3+ charge .
Hence it’s symbol is,
$_{79} ^{197}Au^{3+}$
c)
The number of protons(p) = 34, hence atomic number is 34 and it denotes Selenium (Se).
Mass number = p + n = 34 + 45 = 79
p = e = 34, means atom is neutral.
Hence it’s symbol is,
$_{34} ^{79}Se$
d)
The number of protons(p) = 56 hence atomic number is 56 and it denotes Barium (Ba).
Mass number = p + n = 56 + 80 = 136
p = e = 56, means atom is neutral.
Hence it’s symbol is,
$_{56} ^{136}Ba$
