Question

the number at the beginning of a chemical symbol or formula that indicates the number of units of the substance
product
element
yield
coefficient
a group of numbers and symbols indicating the number and types of atoms chemically bonded in one unit of a substance
empirical formula
coefficient
chemical bond
chemical formula
a chart that organizes the chemical elements by their similar properties
group
product
activity series of metals
periodic table

Explanation:

1. In chemistry, the number at the start of a chemical symbol or formula showing the number of substance units is called a coefficient.
2. A group of numbers and symbols indicating atom - number and types in one substance unit is a chemical formula.
3. A chart organizing chemical elements by similar properties is the periodic table.

Answer:

1. D. coefficient
2. D. chemical formula
3. D. periodic table