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Biology Chapter Two
Terms in this set (26)
the raw materials that make up
the bodies of other organisms, and
the physical environment.
Cells consist of about how much of water
anything that occupies space and has mass (weight) and is composed of chemical elements.
a substance that cannot be broken down to other substances by ordinary chemical means.There are 92 elements in nature—only a few exist in a pure state.
a substance consisting of two or more different elements in a fixed ratio.Sodium chloride, table salt, is a common compound of equal parts of sodium (Na) and chlorine (Cl).
Four elements make up about 96% of the weight of most living organisms. These are
oxygen, carbon, hydrogen, and nitrogen.
essential but are only needed in minute quantities.
Some trace elements are
required to prevent disease.
your body cannot transport oxygen.
An iodine deficiency prevents
production of thyroid hormones, resulting in goiter.
is usually added to municipal water and dental products to help reduce tooth decay.
Several chemicals are added to food to
help preserve it,
make it more nutritious, and/or
make it look better.
is the smallest unit of matter that still retains the properties of an element.
Neutrons and protons are packed Electrons orbit the nucleus.
into an atom's nucleus.
The negative charge of electrons and the positive charge of protons keep
electrons near the nucleus.
The number of protons is
the atom's atomic number.
An atom's mass number is
the sum of the number of protons and neutrons in the nucleus.
The atomic mass is
approximately equal to its mass number.
of an element have the same number of protons but different numbers of neutrons and different isotopes of an element behave identically in chemical reactions.
In radioactive isotopes
the nucleus decays spontaneously, giving off particles and energy.
number of electrons in the outer most shell and determines the chemical properties of the atom
interactions that usually result in atoms staying close together held by attractions
two atoms, each with an unpaired electron in its outer shell actually share a pair of electrons; also connects two hydrogen atoms in a molecule
two or more atoms held together by covalent bonds
attraction for shared electrons
nonpolar covalent bonds
molecules of only one element, the pull toward each atom is equal because each atom has the same electronegativity
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