is a pure substance that cannot be broken down into simpler substances by a chemical reaction.
located on the left side of the periodic table and include 2 transition rows at the bottom. They are shiny solids that are good conductors of heat and electricity. All of them are solids at room temperature except for mercury, which is liquid.
do not have a shiny appearance, and they are generally poor conductors of electricity. They like sulfur and carbon are solids at room temperature.
have properties intermediate between metals and nonmetals. Only seven elements are categorized as this kind of element.
the number of naturally occurring elements
the number of elements prepared by scientists in the laboratory
total number of elements currently known
oxygen, carbon, hydrogen and nitrogen
Comprise 96% of the mass of the human body and are known as the building block elements
needed for hemoglobin
a protein that carries oxygen in red blood cells
the protein that stores oxygen in muscle
needed for proper functioning of many enzymes in liver and kidneys
needed for proper thyroid function
present in body fluids (K, Na, Cl)
Magnesium (Mg) and Sulfur (S)
elements found in proteins
Calcium (Ca) and Phosphorus (P)
present in teeth and bones
amount of each major mineral needed in the daily diet
amount of trace elements needed in the daily diet
a pure substance formed by chemically combining two or more elements together.
consists of element symbols to show the identity of the elements forming a compound and subscripts to show the ratio of atoms (the building blocks of matter) contained in the compound.
is a subatomic particle that holds a positive charge in an atom and is symbolized by p and has a charge that is = +1
is a subatomic particle that holds a negative charge in an atom and is symbolized by e-and has a charge that is = -1
is a subatomic particle that holds no charge in an atom and therefore has a charge that is = 0
a dense core that contains the protons and neutrons. Most of the mass of the atom resides here.
is composed of electrons that move rapidly in the almost empty space surrounding the nucleus. This comprises most of the volume of an atom.
These charges repel.
Atomic Number (Z)
tells us both the number of protons in the nucleus and the number of electrons in the electron cloud of a neutral atom.
Mass Number (A)
= the number of protons (Z) + the number of neutrons.
are atoms of the same element having a different number of neutrons
is the weighted average of the mass of the naturally occurring isotopes of particular element reported in atomic mass units.