Chemistry - Chapter 4

proton

positively charged subatomic particles

atom

the smallest particle of an element that retains its identity in a chemical reaction

mass number

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

atomic mass unit

1/12 the mass of a carbon-12 atom

electron

negatively charged subatomic particle

isotopes

atoms with the same number of protons but different numbers of neutrons

atomic number

the number of protons in the nucleus of an element

atomic mass

the weighted average mass of the atoms in a naturally occurring sample of an element

period

a horizontal row of the periodic table

neutron

subatomic particle with no charge

Dalton’s atomic theory

all elements are composed of atoms, atoms of the same element are alike, atoms that combine do so in simple whole-number ions

nucleus of an atom

positively charged and has a high density

Dalton theorized that atoms are indivisible and that all atoms of an element are identical, but scientists now know that

atoms are divisible

how is the number of neutrons in the nucleus of an atom calculated

subtracting the number of protons from the mass number

what does the sum of protons and neutrons in an atom equal to

mass number

all atoms of the same element have the same what

number of protons

electrons have what charge

negative

what is the charge of the nucleus

positive

where is a neutron found

in the nucleus of an atom

an atom of an element with the atomic number 48 and the mass number of 120 has

48 protons, 48 electrons, and 72 neutrons

how do the isotopes hydrogen-2 and hydrogen-3 differ

hydrogen-3 has two neutrons

the number 80 in the name bromine-80 represents what

mass number

what is the relative atomic masses measured in

amus