ss biology unit 2 part 1 quiz

atom

the smallest unit of an element that retains the element’s properties.

element

a pure substance made of only one type of atom

compound

a substance formed when two or more elements chemically combine in a fixed ratio

mixture

a combination of substances that are physically mixed but not chemically bonded

matter

anything that has mass and takes up space

molecule

two or more atoms chemically bonded together

chemical reaction

involves a change in energy, a process in which substances are changed into new substances

reactants

the starting substances in a chemical reaction

products

the ending materiels produced by a chemical reaction

proton

charge: +1 (positive)
location: nucleus
mass: about 1 atomic mass unit (amu)

neutron

charge: 0 (neutral)
location: nucleus
mass: about 1 atomic mass unit (amu)

electron

charge: -1 (negative)
location: electron cloud outside the nucleus
mass: very small (about 1/1836 of a proton)

energy level (electron shell)

a region around the nucleus where elctron are likely to be found

valence electrons

electrons in the outermost enery level of an atom

first energy level

holds up to 2 eletrons

second energy level

holds up to 8 electrons

third energy level

holds up to 8 electrons

third energy level

holds up to 18 electrons (often simplified to 8 in introductory chemistry)

electron cloud

an atomic onion, has layers called “energy levels”

atomic number

number of protons in an atom’s nucleus, identifies the element.

mass number

total number of protons + neutrons

finding neutrons

mass number- atomic number = number of neutrons

isotope

different versions of the same element that vary by # of neutrons