4.3

number of neutrons ___________________________________

= mass number -atomic number

How are the atoms of one element different from the atoms of another element? How are isotopes of the same element different?

Atoms of different elements are different because they contain different numbers of protons. Isotopes of the same element are different because they have different numbers of neutrons, and thus different mass numbers.

• How do isotopes of an element differ?

Because isotopes of an element have different numbers of neutrons, they also have different mass numbers.

Why is the atomic mass of an element usually not a whole number?

The atomic mass of an element is usually not a whole number because it is a weighted average of the masses of the naturally occurring isotopes of the element.

What information is needed to determine the composition of a neutral atom of any element?

The atomic number and mass number are needed to determine an atom's composition. The atomic number gives the number of protons, which equals the number of electrons. The number of neutrons is the difference between the mass number and the atomic number.

How do you calculate the atomic mass of an element?

To calculate the atomic mass of an element, multiply the mass of each isotope by its natural abundance, expressed as a decimal, and then add the products.

the number of neutrons in an atom is the difference between the mass number and _____________ number.

atomic

________________-:the weighted average of the masses of the isotopes of an element

atomic mass

________________-- (amu): a unit of mass equal to one-twelfth the mass of a carbon-12 atom

atomic mass unit

__________________: the number of protons in the nucleus of an atom of an element

atomic number

Why are atoms with different numbers of neutrons still considered to be the same element?

despite differences in the number of neutrons, isotopes are chemically alike. They have identical numbers of protons and electrons, which determine chemical behavior.

What makes one element different from another?

elements are different because they contain different numbers of protons

atoms of the same element that have the same atomic number but different atomic masses due to a different number of neutrons

isotopes

________________: the total number of protons and neutrons in the nucleus of an atom

mass number

Atomic number is _________----

number of protons and electrons

the number of electrons (negatively charged particles) must equal the number of ____________(positively charged particles).

protons

Mass number = the number of ___________________________________

protons plus the number of neutrons.

Elements are different because they contain different numbers of ___________________ • Because isotopes of an element have different numbers of neutrons, they also have different ________________

protons, MAss numbers

a weighted average mass reflects both the mass and the ______________abundance of the isotopes as they occur in nature.

relative

mass number

subscript