Chemical Interactions

Chapter 1: Atomic Structure and the Periodic Table

Section 1.1

All Atoms are the Smallest Form of

Elements.

All matter is made of atoms.

• All matter is made of atoms.• There are about 100 basic

elements.• Hydrogen is the most

abundant element in Earth’s crust.– It is 90% of the total mass

of the universe– 1% of Earth’s crust.

Continued

• Every element has a unique name.– Names come from many different

sources. Some from Greek, Latin, people, planets, places, etc.

• Each element has a unique symbol.– The first letter is CAPITALIZED.– The second and third are lower case.

•Hydrogen – H•Cobalt – Co•Carbon – C•Unnilpentium - Unp

Each element is made of a different atom.

• John Dalton proposed the first atomic theory in the 1800’s.– Each element is made of tiny

particles called atoms.– Assumed that atoms could NOT

be divided into anything smaller. HE WAS WRONG! Scientists have discovered over 200 subatomic particles.

Continued

• Atoms are made of smaller (subatomic) particles.– Nucleus – At the center of the atom,

contains almost all of the atom’s mass. Contains protons and neutrons.

– Protons – (+) charge, some mass, in the nucleus

– Neutrons – no charge, have mass, in the nucleus

– Electrons – (-) charge, travel on the electron cloud, no mass (very small), neutral atoms have the same number of protons and electrons.

Continued – See page 11

Continued

• Atomic Number: Number of protons in the atom

• Atomic Mass: The number of protons plus the number of neutrons in the nucleus.

• Isotopes: Atoms of the same element with different numbers of neutrons.

Atoms form ions.

• Atoms form ions when they gain or lose electrons.– A gain results in a (-) negative ion– A loss results in a (+) positive ion– Electrons are normally gained or lost

in pairs.– The number of electrons is NOW

different than the number of protons.

Continued – See page 14

• Na has lost one electron:– It is now positively charged (1+)– The positive ion is smaller than the

neutral atom because it has fewer electrons bouncing around.

– The symbol on the ion represents the number of electrons gained (-) or lost (+).

Continued – See page 15

• Chlorine has gained one electron:– It is now negatively charged (1-).– The negative ion is larger than the

neutral atom because it has more electrons bounding around.

Section 1.2Elements Make up the

Periodic Table

Elements can be organized by similarities.

• Dimitri Mendeleev made the first periodic table.

• Atomic mass is used to organize elements.

• Elements with similar properties are placed in the same rows.

The periodic table organizes the atoms of the elements by

properties and atomic number.

• PT organized by atomic number.• Contains the following about each

element.– Atomic number– Chemical symbol– Name– Average atomic mass– State at room temperature

Continued – pg. 22

• Group (Family): a column of elements. – The elements in a group

have similar properties.• Period: a row of elements.

– These elements have chemical properties that tend to change the same way across the table.

Continued – pg. 23

• Properties like atomic size, density, and likelihood to form ions vary in regular ways up, down, and across the periodic table.

Section 1.3

The Periodic Table is a Map of the Elements

The periodic table has distinct regions.

Continue – pg. 26

• Reactivity is indicated by the atoms position on the periodic table.– Groups 1 – 17 are especially

reactive.– Group 18 is least reactive.

Most elements are metals.

• Metals are usually shiny, often conduct electricity and heat well, and can be easily shaped and drawn into wire.

• Mercury is the EXCEPTION, it is a liquid at room temperature (most metals are solids).

Reactive Metals• Alkali Metals: Group 1

– Located at the far left of the periodic table.

– Very reactive– React rapidly with oxygen and water

vapor.• Alkaline Earth Metals: Group 2

– Located at the left of the periodic table.

– Less, but still very reactive.

Continued – pg. 27

Transition Metals• Groups 3 – 12• Generally less reactive than most other

metals.• Include copper, gold, silver, and iron.• Easily shaped

Rare Earth Metals• Located in the top row of the two rows

outside the main body of the periodic table.

• Lanthanides• Not really that rare, just hard to isolate in pure form.

Nonmetals and metalloids have a wide range of

properties.• Nonmetals:

– Located at the right side of the table.

– Include elements with a wide range of properties.

Continued – pg. 29

• Properties vary from one to the other more than the metals.

• Many are gases.• One is a liquid (bromine).• Have dull surfaces.• Cannot be shaped.• Generally poor conductors of

electricity and heat.• Air is made mostly of oxygen and

nitrogen.

Halogens• Group 17.• Salt forming (metal + nonmetal).• Very reactive nonmetals that easily form

compounds called salts with many metals.• Used to kill harmful microorganisms.

– Chlorine in pools.– Iodine in doctor’s offices.

Noble Gases• Group 18• Inert – they almost never react

with other elements.

Metalloids• Lie between metals and nonmetals in

the periodic table.• Have characteristics of metals and

nonmetals.• An important use is in the making of

semiconductors for electronic devices.

Some atoms change their

identity.• Radioactivity

– The nucleus is held together by forces. Sometimes there are too few or too many neutrons in the nucleus, so the forces cannot hold it together properly.

– Energy is released and the nucleus produces particles or rejects particles to regain its stability.

Continued – pg. 30

• If the production of particles changes the number of protons, the atom is transformed into a different element.

• The identity of an element is determined by the number of protons in the nucleus.

• Marie Curie was the first to isolate two radioactive elements.

• Radioactivity is measured with a Geiger counter. The clicks indicate particles being produced.

• Many medical uses for radiation.

Radioactive Decay

• The process of an element being changed into a different element.

• Occurs at a steady rate.– Half-life: time it

takes to transform half of the atoms in a sample to a different element.