Science chapter 1

smallest complete particle of matter containing protons, neutrons and electrons

positively charged particles in the nucleus of an atom

fixed distances from the nucleus of an atom where electrons may be found; they are like steps to a staircase; electrons can only occupy one energy level, not the space in between

neutrally charged particles in the nucleus in an atom

particles that circle around the nucleus in an atom, have a negative charge

the center of an atom, made of subatomic particles called protons and neutrons

is a unique number for each element and indicates the number of protons in that element; also tells you the number of electrons in that element, as they are equal

atoms of the same element that differ in their number of neutrons; isotopes generally have the same physical and chemical properties

sum of the protons and neutrons in an atom; measured in amu, atomic mass unit; tells the mass of the atom; can vary between atoms of the same element depending on the number of neutrons

the average mass of all the isotopes of that element