The Periodic Table

The Periodic Table

Learning Objectives: I can...

• Identify different atoms by the number of protons in the nucleus

• Demonstrate that the number of electrons equals the number of protons in a neutral atom

• Explain the meaning of atomic number and atomic mass

History of the Periodic Table

• In 1869, Russian chemist Dimitri Mendeleev started arranging chemical elements by atomic mass.

• Predicted the discovery of other elements and left spaces in the periodic table for them

Multiple Choice

How was Mendeleev's periodic table arranged?

• by increasing atomic mass

• by decreasing atomic mass

• by increasing atomic number

• by decreasing atomic number

The Periodic Table: First 20 Elements

• Many common substances are composed of atoms from these first 20 elements.

• Each box contains information about a different element

• Shows all the atoms that everything in the known universe is made from

An Example: Carbon

• Atomic Number: Number of protons in the nucleus of the atom

• Atomic mass: the average mass of atoms in an element

• Element Name: Usually from a Greek or Latin word for the element or a substance containing the element.

• Symbol: Short-hand abbreviation for the element name (starts with a capital letter)

Multiple Choice

What is the atomic mass of

iron (Fe)?

• 26

• 13

• 55.845

• 23.423

Multiple Choice

What is the atomic number of Sulfur?

• 16

• 2

• 32.065

• 86

Atomic Mass

• Based on the mass of the protons, neutrons and electrons of that element.

• Mass of the proton and neutron are about the same, but the mass of the electron is much smaller

• Majority of the atomic mass is contributed by the protons and neutrons

Atomic Mass

• For any element in the periodic table, the number of electrons in an atom always equals the number of protons in the nucleus

• Not true for neutrons

• Atoms of the same element can have different numbers of neutrons than protons.

• They are called isotopes.

• Atomic mass is the average of the atomic mass of the isotopes of an element.

Carbon

• Vast majority of carbon atoms have 6 protons and 6 neutrons

• A small percentage have 6 protons and 7 neutrons

• An even smaller percentage have 6 protons and 8 neutrons

• Since the majority of carbon atoms have a mass very close to 12, the average atomic mass is slightly greater than 12.

• 
  

Multiple Choice

Isotopes of an element have a different number of...

• Protons

• Neutrons

• Electrons

• Mass

Subatomic Particles

• Proton: positively charged particle; located in the nucleus; is the atomic number

• Electron: negatively charged particle surrounding the nucleus; equal to the number of protons

• Neutron: No charge; has almost the same mass as a proton; equal to or slightly greater than the number of protons

• 
  

Multiple Choice

How many protons are in Sodium?

• 11

• 22

• 12

• 33

Multiple Choice

What does this number represent?

• Number of protons
• Number of neutrons
• Number of electrons
• Number of protons and neutrons

Multiple Choice

What is the atomic weight of Iron?

• 26
• 55.845
• 56
• 30

Multiple Choice

What is the atomic mass of Gold?

• 79
• 196.9665
• 117
• 275

Multiple Choice

How many protons are in Beryllium?

• 4
• 9
• 5
• 2

Multiple Choice

What is the atomic mass of Neon?

• 10

• 20.18

• 10.18

• 9.82

Multiple Choice

Elements can have the same number of protons?

• True
• False

Multiple Choice

The following element key shows how many protons?

• 16
• 15.999
• Oxygen
• 8

Multiple Choice

Where is the proton located?

• In the very dense nucleus
• Floating around in the negative electron cloud
• the loose nucleus
• the positive electron cloud

Multiple Choice

Sodium has an atomic number of 11, how many protons does this atom have?

• 22
• 11
• 12
• 2

Multiple Choice

What is the chemical symbol for the element oxygen

• O
• Oxy
• ox
• Oy

Multiple Choice

What is the chemical symbol for the element hydrogen

• H
• He
• h
• he

Multiple Choice

The number at the top of each square on the periodic table is the ...

• atomic number
• atomic mass
• Chemical Symbol
• Element Name

Multiple Choice

The atomic number tells you what?

• number of electrons
• number of protons
• number of neutrons
• both electrons and protons in an atom.

Multiple Choice

What does the 1.00794 stand for?

• Hydrogen
• atomic number
• atomic mass
• atomic explosion

Multiple Choice

What is at the center of every atom?

• An electron

• A compound

• A molecule

• A nucleus

Multiple Choice

Which two particles make up the nucleus of an atom?

• Protons and Electrons
• Protons and Neutrons
• Molecules and Compounds
• Neutrons and Electrons