Ch. 4, Sec. 2 Study Questions
What is an isotope?
An atom of an element with a different number of neutrons
What is an ion?
An atom that has gained or lost electrons and thus has an electric charge
What is the charge of an unreacted atom?
Neutral - no charge
Explain how the electric force holds atoms together.
The positively charged protons are attracted to the negatively charged electrons
Why do unreacted atoms have no charge?
Their number of protons equals their number of electrons, so the positive and negative charges cancel each other out
How do you calculate the molar mass of a compound?
add the masses of all of the atoms in one molecule of the compound
When an atom gains or loses electrons, what is formed?
an ion
What is the number of protons in an atom?
atomic number
How can you calculate the number of neutrons in an atom?
by subtracting the atomic number from the mass number
Which subatomic particles has a negative charge?
electron
Of the three subatomic particles, which has the smallest mass?
electrons
What is an atom of an element with a different number of neutrons?
isotope
What are radioisotopes?
isotopes that decay (break down) over time to form a different isotope of the same element
What is the total number of protons and neutrons in the nucleus of an atom?
mass number
Why are atomic masses an average?
more common isotopes affect the average more than less abundant isotopes
What charge does an electron have?
negative
Which subatomic particle has no charge?
neutron
What charge does a neutron have?
no charge - neutral
What charge does a proton have?
positive
Which subatomic particle has a positive charge?
proton
Each element has a unique number of...
protons
What two subatomic particles cause unreacted atoms to have no charge?
protons & electrons
Of the three subatomic particles, which two are nearly identical in size and mass?
protons & neutrons
Which two types of subatomic particles are located in the nucleus?
protons & neutrons
What are isotopes that break down (decay) over time to form a different isotope of the same element?
radioisotopes
What is the electric force?
the attraction between positive and negative charges
What force holds atoms together?
the electric force
What is the mass number?
the number of protons and neutrons in the nucleus of an atom
What is the atomic number?
the number of protons in an atom
How can elements of the same atom have different mass numbers?
they can have different numbers of neutrons
What do all atoms of a given element have in common?
they have the same number of protons
What unit is used to describe the masses of atoms?
unified atomic mass unit (u)
