lecture 2

anything that occupies space and has mass

is the quantity of matter an object has

defined as the force produced by gravity acting on mass.

are substances that cannot be broken down chemically into simpler kinds of matter. More than 100 elements have been identified, though fewer than 30 are important to living things

more than 90 percent of the mass of all kinds of living things is composed of combinations of just four elements

Information about the elements is summarized on a chart

Most of the other symbols are derived from the _____ names of elements

The simplest particle of an element that retains all of the properties of that element

Central region. Makes up the bulk of the mass of the atom and consists of two kinds of subatomic particles

positively charge

Negative charge

numbers of protons in an atom of the element

an atom is equal to the total number of protons and neutrons of the atom.

high-energy particles that have very little mass

is a three-dimensional region around a nucleus that indicates the probable location of an electron.

Atoms of the same element that have a different number of neutrons

an element takes into account the relative amounts of each isotope in the element, and this average is the mass found in the periodic table.

made up of atoms of two or more elements in fixed proportions

do not react with other elements under normal conditions.

attractive forces that hold atoms together.

forms when two atoms share one or more pairs of electrons

simplest part of a substance that retains all of the properties of that substance and can exist in a free state.

An atom or molecule with an electrical charge

positive and negative electrical charges attract each other, the sodium ion and the chloride ion attract each other