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Bio 2.1,2.3,.2.5, 2.6
Terms in this set (21)
Matter is defined as anything that has space and has mass.
An element is a substance that cannot be broken down to other substances by ordinary means.
A compound is a substance consisting of two or more different elements combined in a fixed ratio.
The trace elements (Boron, Chromium, Cobalt, Copper, Fluorine, Iodine, Iron, Manganese, Zinc, Tin, Molybenum, Selenium, Silicon, Vanadium) are essential for humans, but only in minute quantities.
An atom, named from a Greek word meaning "indivisible", is the smallest unit of matter that still retains the properties of an element.
A proton is the subatomic particle with a single positive electrical charge.
An electron is a subatomic particle with a single negative charge.
A neutron, as it name implies, is electrically neutral (has no charge).
Notice that two protons and two neutrons are tightly packed in the atom's central core, or nucleus.
All atoms of a particular element have the same unique number of protons. This number is the element's atomic number.
An atom's mass number is the sum of the number of protons and neutrons in its nucleus.
Thus, an atom's atomic mass is approximately equal to its mass number- the sum of its protons and neutrons in daltons.
The different isotopes of an element have the same number of protons and behave identically in chemical reactions, but they have different numbers of neutrons.
A radioactive isotope is one in which the nucleus decays spontaneously, giving off particles and energy.
It turns out that electrons can be located in different electron shells, each with a characteristic from the nucleus.
Theses interaction usually result in atoms staying close together, held by attractions known as chemical bonds.
In a covalent bond, two atoms, each with an unpaired electron in its outer shell, actually share a pair of electrons.
Atoms held together by covalent bonds form a molecule.
An atom's attraction for shared electrons is called its electronegativity.
Nonpolar Covalent Bonds
The bonds in such molecules are said to be non polar covalent bonds because the electrons are shared equally between the atoms.
Polar Covalent Bonds
This unequal sharing of electrons produces a polar covalent bond.
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