Chapter 2 Review: Intro to Atomic Structure & Periodicity

The Law of Conservation of Mass

in a chemical reaction, matter is neither created nor destroyed

The Law of Definite Proportions

all samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements

The Law of Multiple Proportions

when two elements form two different compounds, the masses of element B that combine with 1 gram of element A can be expressed as a ratio of small whole numbers

J.J. Thomson

discovered the electron

electron

a negatively charged, low-mass particle present within all atoms

the charge of the proton and the electron are..

equal in magnitude but opposite in sign

Avogadro’s Number

1 mole = 6.02214 × 10²³ particles

molar mass

the mass of 1 mol of atoms of an element

mass number (A)

the sum of the number of neutrons and protons in an atom

atomic mass

represents the average mass of the isotopes that compose that element; directly beneath the element’s symbol in the periodic table

cations

positively charges ions

anions

negatively charged ions

noble gases

the group 8A elements that are mostly unreatcive

alkali metals

have one more electron than the previous noble gas. in their reactions, they tend to lose one electron, resulting in the same electron configuration as a noble gas

alkaline earth metals

the group 2A elements. tend to lose two electrons, resulting in the same electron configuration as a noble gas

halogens

the group 7A elements, very reactive nonmetals. in their reactions with metals, tend to gain an electron and attain the electron configuration of the next noble gas