Atomic Structure Notes You will need your periodic table or your textbook p. 28

Atomic Structure I.“Basic Building Blocks” of Matter A. Atoms are considered to be the basic building blocks of matter 1. Scientists now know that atoms are made up of three subatomic particles called protons, neutrons, and electrons.

Protons (p +) – positively charged subatomic particles that are found in the nucleus of an atom (mass – 1 amu) Neutrons (n) – neutral subatomic particles that are found in the nucleus of an atom (mass = 1 amu) Electrons (e - ) – negatively charged subatomic particles that are found in the space outside the nucleus of an atom (no significant mass)

2.The nucleus of an atom is located in the center of the atom and contains most of the mass of the atom The electrons are located in the space around the nucleus called the electron cloud. 3. Even though most of the mass of an atom is in its nucleus the majority of the space is empty in the electron cloud.

B.We can describe subatomic particles by their mass, electric charge, and location in the atom. Properties of Subatomic Particles ParticleRelative ChargeMass (amu) Proton (p + )+11 Neutron (n)01 Electron (e - )0

II.Atomic Number and Mass Number A. Atoms of different elements have different atomic numbers. Atomic number – total number of protons in the nucleus of an atom of a given element B. This means each element has its own atomic number and you can determine which element an atom is by the number of protons in its nucleus.

C. Since each element has a different number of protons, atoms of each element have different masses (in the nucleus). Mass number (atomic mass) – the total number of protons and neutrons found in the nucleus of an atom (atomic mass/molar mass rounded to a whole number)

Atomic number and mass number are different because the atomic number is only the number of protons in an atom and the mass number includes the number of neutrons as well.

D. We can use the atomic number and mass number of an atom to determine the number of protons, electrons, and neutrons in the atom. # Protons = atomic number #Electrons = the number of protons (when the atom is neutral) #Neutrons = mass number – atomic number

Write this example on the back of your notes Example: Carbon (C) Atomic Number = Mass Number = #Protons = #Electrons = #Neutrons = (mass number) – (atomic number) =

Write this example on the back of your notes Example: Carbon (C) Atomic Number = 6 Mass Number = 12 #Protons = 6 #Electrons = 6 #Neutrons = (mass number) – (atomic number) = (12) – (6) = 6

E. Ions are formed when the number of protons and electrons in an atom are not the same. Ion – an atom or group of combined atoms that has a charge because of the loss or gain of electrons

1. The number of protons cannot change when ions are formed but electrons can be gained. When an atom gains one electron it has a 1 - charge When an atom gains two electrons it has a 2 - charge When an atom gains three electrons it has a 3 - charge

1. The number of protons cannot change when ions are formed but electrons can be lost. When an atom loses one electron it has a 1 + charge When an atom loses two electrons it has a 2 + charge When an atom loses three electrons it has a 3 + charge

Now take out the practice worksheet: Atomic Structure Practice

1.Helium Atomic Number: Mass Number: #Protons: #Neutrons: #Electrons:

1.Helium Atomic Number: 2 Mass Number: 4 #Protons: 2 #Neutrons: 4 – 2 = 2 #Electrons: 2

2.Aluminum Atomic Number: Mass Number: #Protons: #Neutrons: #Electrons:

2.Aluminum Atomic Number: 13 Mass Number: 27 #Protons: 13 #Neutrons: 27 – 13 = 14 #Electrons: 13

3. Magnesium Atomic Number: Mass Number: #Protons: #Neutrons: #Electrons:

3. Magnesium Atomic Number: 12 Mass Number: 24 #Protons: 12 #Neutrons: 24 – 12 = 12 #Electrons: 12

4.Lithium Atomic Number: Mass Number: #Protons: #Neutrons: #Electrons:

4.Lithium Atomic Number: 3 Mass Number: 7 #Protons: 3 #Neutrons: 7 – 3 = 4 #Electrons: 3

Element Name SymbolAtomic Number Mass Number Number of Electrons Number of Protons Number of Neutrons Molar Mass (g) aluminumAl bismuth calcium20 copper