Atoms & Molecules for Environmental Science

Atoms building blocks of matter Smallest particle that retains its properties dense nucleus in center –mostly space

Subatomic Particles particlesizechargelocation protonlargepositivenucleus neutronlargeneutralnucleus electronsmall(1/2000 th )negativecloud

Electrons in energy levels –Electrons with the most energy are farthest from the nucleus outermost determine characteristics –React to form bonds

Symbols to Memorize

Atomic Number Atomic # = # of Protons (whole number) = # of electrons in a neutral atom –gives identity

Atomic Mass Atomic mass number = weighted average of the masses of the isotopes of the element (decimal)

mass number= # of protons + # of neutrons – 12 C has 6 protons + 6 neutrons – 13 C has 6 protons + 7 neutrons

Isotopes atoms of the same element with a different mass – 12 C – 13 C – 14 C

Draw an atom of 1 H. 1 H has 1 proton 0 neutrons 1 electron 1P e-e-

Draw an atom of 6 Li. Li has 3 protons 3 neutrons 3 electrons 3P 3N e - e-e-

How many electrons do you predict will be in the outer energy level of sodium? Draw an atom of 21 Na. Sodium has 11 protons 10 neutrons 11 electrons 11P 10N e-e- e-

Draw an atom of 20 Mg. Magnesium has 12 protons 8 neutrons 12 electrons 12P 8N e-e-

In square 5 draw an atom of 20 Ne. Neon has 10 protons 10 neutrons 10 electrons 10P 10N e-e-

Draw the isotopes 14 C and 12 C. Carbon 12 has 6 protons 6 neutrons 6 electrons Carbon 14 has 6 protons 8 neutrons 6 electrons 6P 6N 6P 8N e-e- e-

Stable Atoms have eight electrons in s & p orbitals in the outermost energy level do not go through chemical reactions Noble gases