Inside the Atom~Notes

Structure of the Atom There are two regions The nucleus With protons and neutrons Positive charge Almost all the mass Electron cloud- Most of the volume of an atom The region where the electron can be found

Subatomic particles Electron Proton Neutron Name Symbol Charge Relative mass Actual mass (g) e - p + n 0 -1 +1 0 1/1840 1 1 9.11 x 10 -28 1.67 x 10 -24 1.67 x 10 -24

Size of an atom Atoms are small. Measured in picometers, 10 -12 meters Hydrogen atom, 32 pm radius Nucleus tiny compared to atom IF the atom was the size of a stadium, the nucleus would be the size of a marble. Radius of the nucleus near 10 -15 m. Density near 10 14 g/cm

Counting the Pieces Atomic Number = number of protons # of protons determines kind of atom the same as the number of electrons in the neutral atom Mass Number = the number of protons + neutrons All the things with mass

Symbols Contain the symbol of the element, the mass number and the atomic number THIS IS NOT THE SAME AS WHAT IS IN THE PERIODIC TABLE! X Mass number Atomic number

Symbols Find the number of protons number of neutrons number of electrons Atomic number Mass Number F 19 9

Symbols Find the number of protons number of neutrons number of electrons Atomic number Mass Number Br 80 35

Symbols if an element has an atomic number of 34 and a mass number of 78 what is the number of protons number of neutrons number of electrons Complete symbol

Symbols if an element has 91 protons and 140 neutrons what is the Atomic number Mass number number of electrons Complete symbol

Ions Under normal conditions, atoms have the same number of electrons as protons When atoms react chemically, they can gain or loose electrons When an atom has gained or lost an electron it is now considered an ion

A neutral atom of sodium has 11 protons and 11 electrons When sodium reacts chemically, it typically looses one electron; giving it 11 protons and 10 electrons Remember: each proton has a positive charge + each electron has a negative charge - Sodium ION with 11 protons (11 +) and 10 electrons (10-) Now has a NET charge of (1+)

A neutral atom of chlorine has 17 protons and 17 electrons When chlorine reacts chemically, it typically gains one electron; giving it 17 protons and 18 electrons Remember: each proton has a positive charge + each electron has a negative charge - Chlorine ION with 17 protons (17 +) and 18 electrons (18-) Now has a NET charge of (1-)

A neutral atom of lithium has 3 protons and 3 electrons When lithium reacts chemically, it typically looses one electron; giving it 3 protons and 2 electrons Remember: each proton has a positive charge + each electron has a negative charge - Lithium ION with 3 protons (3 +) and 2 electrons (2-) Now has a NET charge of (1+) 1 + Li 3 6 Li 3 6

1 + If no charge here: ATOM NEUTRAL (same number of protons as electrons) If charge here: ION Pos charge = more protons than electrons Neg charge = more electrons than protons Li 3 6 Li 3 6

Isotopes Dalton was wrong. Atoms of the same element can have different numbers of neutrons different mass numbers called isotopes 3 protons; 3 neutrons Mass # 6 3 protons; 4 neutrons Mass # 7 BOTH Li

Naming Isotopes Put the mass number after the name of the element carbon- 12 carbon -14 uranium-235

Atomic Mass How heavy is an atom of oxygen? There are different kinds of oxygen atoms. More concerned with average atomic mass. Based on abundance of each element in nature. Don’t use grams because the numbers would be too small

Measuring Atomic Mass Unit is the Atomic Mass Unit (amu) One twelfth the mass of a carbon-12 atom. Each isotope has its own atomic mass we need the average from percent abundance.

Atomic Mass Calculate the atomic mass of copper if copper has two isotopes. 69.1% has a mass of 62.93 amu and the res has a mass of 64.93 amu.

Atomic Mass Magnesium has three isotopes. 78.99% magnesium 24 with a mass of 23.9850 amu, 10.00% magnesium 25 with a mass of 24.9858 amu, and the rest magnesium 25 with a mass of 25.9826 amu. What is the atomic mass of magnesium? If not told otherwise, the mass of the isotope is the mass number in amu

Atomic Mass Is not a whole number because it is an average. are the decimal numbers on the periodic table. 6 C 12.01

11 protons; 10 electrons 16 protons; 18 electrons 13 protons; 10 electrons Na 11 23 + S 16 32 2- Al 13 27 3+

How Many Protons, Neutrons, and Electrons???? N 7 14 3- Ca 20 41 2+ Cl 17 33 1-

Inside the Atom~Notes

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Inside the Atom~Notes