Answer
Identifying the elements with the given atomic numbers, and stating the number of protons and electrons in the
neutral atom:
common formulae used:
The atomic number = The number of protons
The number of protons = The number of electrons
a) 2
Helium (He) is the element with 2 as its atomic number.
A neutral helium atom has 2 protons and 2 electrons.
b) 11
Sodium (Na) is the element with 11 as its atomic number.
A neutral sodium atom has 11 protons and 11 electrons.
c) 20
Calcium (Ca) is the element with 20 as its atomic number.
A neutral calcium atom has 20 protons and 20 electrons.
d) 47
Silver (Ag) is the element with 47 as its atomic number.
A neutral silver atom has 47 protons and 47 electrons.
e) 78
Platinum (Pt) is the element with 78 as its atomic number.
A neutral platinum atom has 78 protons and 78 electrons.
Work Step by Step
The atomic number = The number of protons
The number of protons = The number of electrons
Refer to the periodic table to find the names of the elements.
