CAMPBELL-BIOLOGY-IN-FOCUS CHAPTERS 2 12 EDITION EXAM Q’S AND A’S

CAMPBELL-BIOLOGY-IN-FOCUS CHAPTERS 2 12 EDITION EXAM Q’S AND A’S Matter - answer- Anything that has mass and takes up space Element - answer- A substance that cannot be broken down into simpler substances Compound - answer- substance formed by the chemical combination of two or more elements in definite proportions essential elements - answer- A chemical element required for an organism to survive, grow, and reproduce. trace elements - answer- An element indispensable for life but required in extremely minute amounts. Atoms - answer- smallest unit of matter Nuetrons - answer- Neutral particles that don't have an electric charge Protons - answer- Positively charged particles Electrons - answer- Negatively charged particles atomic nucleus - answer- An atom's dense central core, containing protons and neutrons. Dalton - answer- A measure of mass for atoms and subatomic particles; the same as the atomic mass unit, or amu. atomic number - answer- the number of protons in the nucleus of an atom Atomic mass - answer- The average mass of all the isotopes of an element Isotopes - answer- One of several atomic forms of an element, each with the same number of protons but a different number of neutrons, thus differing in atomic mass. half-life - answer- length of time required for half of the radioactive atoms in a sample to decay radioactive isotope - answer- An isotope (an atomic form of a chemical element) that is unstable; the nucleus decays spontaneously, giving off detectable particles and energy. radiometric dating - answer- method used to determine the age of rocks using the rate of decay of radioactive isotopes Energy - answer- The capacity to cause change, especially to do work (to move matter against an opposing force). potential energy - answer- stored energy that results from the position or shape of an object electron shell - answer- an energy level of electrons at a characteristic average distance from the nucleus of an atom valence electrons - answer- The electrons in the outermost shell (main energy level) of an atom; these are the electrons involved in forming bonds. valence shell - answer- The outermost energy shell of an atom, containing the valence electrons involved in the chemical reactions of that atom. Chemical bonds - answer- An attraction between two atoms, resulting from a sharing of outer-shell electrons or the presence of opposite charges on the atoms. The bonded atoms gain complete outer electron shells. covalent bond - answer- a bond formed when atoms share one or more pairs of electrons Molecule - answer- two or more atoms held together by covalent bonds single bond - answer- a covalent bond in which one pair of electrons is shared between two atoms double bond - answer- A covalent bond in which two pairs of electrons are shared between two atoms Valence - answer- The bonding capacity of a given atom; the number of covalent bonds that an atom can form, which usually equals the number of unpaired electrons in its outermost (valence) shell. Electronegativety - answer- The attraction of a given atom for the electrons of a covalent bond. non polar covalent bond - answer- a covalent bond in which the bonding electrons are shared equally by the bonded atoms, resulting in a balanced distribution of electrical charge polar covalent bond - answer- A covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive. Ions - answer- positively and negatively charged atoms Cation - answer- A positively charged ion Anion - answer- A negatively charged ion ionic bond - answer- A chemical bond resulting from the attraction between opposite