The Atom

Chm 1.1.1

Essential Standards

• Chm 1.1.1• Characterize the protons, neutrons, electrons

by location, relative charge, relative mass (p=1, n=1, e=1/2000.)

• Use symbols A=mass number, Z=atomic number

What is an atom?

• The smallest particle of an element that retains its identity in a chemical reaction

Sizing up the atom

• Read pg. 103 silently

Subatomic particle

• 3 kinds of subatomic particles• Electrons, protons, and neutrons

electrons

• Negatively charges subatomic particles• e-

protons

• Positively charged

neutrons

• No charge or neutral

nucleus

• Each atom contains a nucleus • Inside the nucleus are protons and neutrons• Outside the nucleus is electrons

Chart

• See chart pg. 106• Please copy in notes-change 1840 to 2000• Which subatomic particle is the smallest?

Mass number and atomic number

• Elements are different because they contain different numbers of protons

• The atomic number is the number of protons in the nucleus in the atom in that element

• The symbol for atomic number is Z• The atomic number identifies the element and

can be found on the periodic table

Atomic number

• Ex. Atomic number or Z for Oxygen=8• Sulfur, Z=16• Hydrogen, Z=1• You try…• Boron (B), Z=?• Chlorine (Cl), Z=?

Mass number

• The total number of protons + neutrons in an atom

• See table on page 110• Add the number of protons and neutrons and

see if that equals the mass number

Mass number

• Can be found on periodic table• mass number or A of Hydrogen (H)=1.00794• Sulfur (S), A=32.066• Chlorine (Cl), A=35.453• You try…• Lithium (Li), A=?• Sodium (Na), A=?

Mass number

• The number of neutrons in an atom is the difference between the mass number and atomic number

• Number of neutrons= mass # - atomic #• Let’s try oxygen• Neutrons = 16-8• Neutrons=8

Mass number

• Number of neutrons= mass # - atomic #• How many neutrons does Chlorine (Cl)have?

notation

• The composition of any atom can be represented in shorthand notation using atomic # and mass #

• The chemical symbol Au appears with 2 numbers written to its left

• The atomic number is subscript• The mass number is superscript• Ex. 197/79 Au=Gold or gold-197

Try it out

• Practice pg 112