Answer:
1. hydrogen - H
2. helium - He
3. sodium - Na
4. magnesium - Mg
5. potassium - K
Explanation:
Hydrogen is the element of group 1 and first period. The atomic number of hydrogen is 1 and the symbol of the element is H.
The electronic configuration of the element hydrogen is:-

Helium is the element of group 18 and first period. The atomic number of helium is 2 and the symbol of the element is He.
The electronic configuration of the element helium is:-

Sodium is the element of group 1 and third period. The atomic number of sodium is 11 and the symbol of the element is Na.
The electronic configuration of the element sodium is:-

Magnesium is the element of group 2 and third period. The atomic number of magnesium is 12 and the symbol of the element is Mg.
The electronic configuration of the element magnesium is:-

Potassium is the element of group 1 and forth period. The atomic number of potassium is 19 and the symbol of the element is K.
The electronic configuration of the element potassium is:-

Explanation:
firstly find for the molar mass of kcl and molar mass of k
and then
molar mass of k = x
molar mass of kcl= 40
cross mutiply and then simplify you will get your answer
Answer:
Energy equals mass times the speed of light squared.
Explanation:
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Answer:

Explanation:
1. Volume of sealed tube
Assume the sealed tube is a right circular cylinder in which the cap and the base are also 4.20 mm thick.
Its outside dimensions are 155 mm long × 10.0 mm diameter.
Its inside dimensions are
h = 155 mm - 2 × 4.20 mm = 146.6 mm
r = 5.0 mm - 4.20 mm = 0.8 mm
V = πr²h = π(0.8)²× 146.6 mm³ = 294.8 mm³ = 0.2948 cm³
2. Calculate the mass of NH₃