Science Exam Study {Unit 4 Elements and the Periodic table}

Atoms

Atoms

smallest unit of matter

Nucleus

Control center of the cell

Protons

Positively charged particles

Neutrons

neutral charge

Electrons

Negatively charged particles

atomic number

number of protons in the nucleus
the top number on the periodic table

atomic mass number

sum of number of protons and number of neutrons
on the periodic table its the bottom number

Isotopes

atoms of same element with different numbers of neutrons but same number of protons

Periodic Table

arrangement of elements according to repeated changes in properties

Period

horizontal row in the periodic table

Groups

Vertical columns on the periodic table also called families

Properties of Metals

shiny, good conductors of heat an electricity, malleable

Properties of Non-Metals

poor conductors of heat and electricity, mostly gases

except for carbon, iodine and sulfur are sloid non metals

nobal gases

group 18-Classified under non-metals
vary unreactive

Halogens

Group 17 highly reactive

Metalloids

Elements that have properties of both metals and nonmetals.

Reactivity of Elements

elements in the periodic table react with other elements by gaining, losing or sharing valence electrons

Valence electrons

Electrons on the outermost shell of an atom

Radioactivity

the process in which an unstable atomic nucleus loses energy by emitting radiation.
the measurement unit of radioactivity is the Bequerel

Alpha Radiation

large positive particles that does not penetrate vary deeply

beta radiation

Fast-moving electrons. Moderately penetrating

Gamma Radiation

High energy waves similar to X-rays Highly penetrating and dangerous for humans