Chapter 2 Flashcards
matter
anything that occupies space and has mass.
mass
the amount of matter in an object
weight
the gravitational force acting on an object of a given mass.
kilogram ( kg )
the international unit for mass
gram (g)
1/1000 the mass of a kilogram
element
the simplest type of matter, having unique chemical properties.
atom
the smallest particle of an element that has the chemical characteristics of that element.
neutron
has no electrical charge
proton
has one positive charge
electron
has one negative charge
nucleus
protons and neutrons form the nucleus at the center of an atom; electrons move around the nucleus; nucleus accounts for 99.97% of an atom’s mass but only 1 ten-trillionth of its volume; most of the volume of an atom is occupied by the electrons.
electron cloud
the region where the electron is most likely to be found
atomic number
equal to the number of protons in each atom and, because the number of electrons is equal to the number of protons,
the atomic number is also the number of electrons.
mass number
the number of protons plus the number of neutrons in each atom.
Isotopes
two or more forms of the same element that have the same number of protons and electrons but a different number of neutrons
dalton (Da)
a system of relative atomic mass scientists use to avoid working with such small numbers; unified atomic mass unit ( u ) is 1/12 the mass of 12 C, a carbon atom with 6 protons and 6 neutrons. Thus, 12 C has an atomic mass of exactly 12 Da.
atomic mass
the average mass of an element’s naturally occurring isotopes, taking into account the relative abundance of each isotope.
Avogadro’s number or 1 mole (mol)
chemist groups atoms in lots of 6.022 x 10 ^23
molar mass
The mass of 1 mole of a substance expressed in grams
chemical bonding
When the outermost electrons are transferred, or shared, between atoms; the outermost electrons of an atom determine its chemical behavior.
ion
a charged particle, formed when an atom loses or gains electrons resulting in unequal numbers of protons and electrons
cations
Positively charged ions
anions
negatively charged ions
ionic bond
a bond when a cation and anion is bonded together; cations and anions tend to remain close together because oppositely charged ions are attracted to each other