Explain how to count the number of elements in a compound

The number of elements in a compound is counted by identifying and counting the chemical symbols represented in the chemical formula

A compound is a substance that is a mixture of more than one elements.

Compounds are made of two or more elements. These elements are represented by their symbols. These symbols can be identified and the number of elements represented by these symbols are counted.

For example, in the compound :

H represents Hydrogen

O represents Oxygen

The elements in Water ( ) are Hydrogen and Oxygen

Therefore, the number of elements in   is 2

Also in,

The elements are Sodium(Na) and Chlorine(Cl)

There are two elements in NaCl

Hence, the number of elements in a compound is counted by identifying and counting the chemical symbols represented in the chemical formula

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Using the formula cards again, add the coefficient of 2 in front of the formula and have them recalculate the number of each element and the total number of atoms in each element.

Explanation:

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.