# Do you round mass number up or down?

## Do you round mass number up or down?

The mass number can be found by rounding the average atomic mass to the nearest whole number. For example, the average atomic mass of lithium is 6.941 amu. The mass number of lithium is 7 (6.941 rounds to 7).

## Does mass go up the periodic table?

The periodic table of elements arranges all of the known chemical elements in an informative array. Elements are arranged from left to right and top to bottom in order of increasing atomic number. Order generally coincides with increasing atomic mass.

Do you round off molar mass?

As a rule of thumb, always use the value rounded to two digits after the decimal point. Example 2: One periodic table lists the molar mass of Chlorine to be 35.453 grams per mole. Round this to the correct number of digits.

### How do you use the periodic table?

Scientists use the periodic table to quickly refer to information about an element, like atomic mass and chemical symbol. The periodic table’s arrangement also allows scientists to discern trends in element properties, including electronegativity, ionization energy, and atomic radius.

### What are the numbers on a periodic table?

In the modern periodic table, the elements are listed in order of increasing atomic number. The atomic number is the number of protons in the nucleus of an atom. The number of protons define the identity of an element (i.e., an element with 6 protons is a carbon atom, no matter how many neutrons may be present).

What happens to the mass number as you go through the periodic table?

Explanation: As you move across a period, the atomic mass increases because the atomic number also increases. The atomic mass for any given atom mainly comes from the mass of the protons and neutrons.

#### Do you use sig figs when calculating molar mass?

The first rule is to use four digits in atomic weights and consider the calculated formula or molar mass as given with four significant digits. The uncertainty is rounded up to one (two) significant digit(s), and the formula or molar mass is rounded to the same absolute accuracy as the rounded uncertainty.

#### How do you round moles?

Convert the mass of each element to moles using the molar mass from the periodic table. Divide each mole value by the smallest number of moles calculated. Round to the nearest whole number. This is the mole ratio of the elements and is represented by subscripts in the empirical formula.