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
a)
The number of protons(p) = 24, hence atomic number is 24 and it denotes Chromium (Cr).
Mass number = p + n = 24 + 28 = 52
p = e = 24, means atom is neutral.
Hence it’s symbol is,
$_{24} ^{52}Cr$
b)
The number of protons(p) = 20, hence atomic number is 20 and it denotes Calcium (Ca).
Mass number = p + n = 20 + 20 = 40
p = e = 20, means atom is neutral.
Hence it’s symbol is,
$_{20} ^{40}Ca$
c)
The number of protons(p) = 33, hence atomic number is 33 and it denotes Arsenic (As).
Mass number = p + n = 33 + 42 = 65
p = e = 33, means atom is neutral.
Hence it’s symbol is,
$_{33} ^{65}As$
d)
The number of protons(p) = 53 hence atomic number is 24 and it denotes Iodine (I).
Mass number = p + n = 53 + 74 = 127
p = e = 53, means atom is neutral.
Hence it’s symbol is,
$_{53} ^{127}I$
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
a)
The number of protons(p) = 24, hence atomic number is 24 and it denotes Chromium (Cr).
Mass number = p + n = 24 + 28 = 52
p = e = 24, means atom is neutral.
Hence it’s symbol is,
$_{24} ^{52}Cr$
b)
The number of protons(p) = 20, hence atomic number is 20 and it denotes Calcium (Ca).
Mass number = p + n = 20 + 20 = 40
p = e = 20, means atom is neutral.
Hence it’s symbol is,
$_{20} ^{40}Ca$
c)
The number of protons(p) = 33, hence atomic number is 33 and it denotes Arsenic (As).
Mass number = p + n = 33 + 42 = 65
p = e = 33, means atom is neutral.
Hence it’s symbol is,
$_{33} ^{65}As$
d)
The number of protons(p) = 53 hence atomic number is 24 and it denotes Iodine (I).
Mass number = p + n = 53 + 74 = 127
p = e = 53, means atom is neutral.
Hence it’s symbol is,
$_{53} ^{127}I$
