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Chemistry�(HOLT Chapter 4)

Atoms and the Periodic Table

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Day One Notes

Atoms

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Chemistry:

The study of composition, structure and properties of matter and changes that happen to matter

Matter:

Anything that has mass and occupies space
Solid, Liquid, Gas, or plasma

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Elements Contain a Single Kind of Atom

Atom:

Atoms make up the matter around you
Substances are created as a result of the combination of many atoms
Atoms are very small

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Subatomic particles � (parts of the atom):

1. Proton = (+) Charge

2. Electron = (-) Charge

Neutron = neutral (no) charge

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Atomic Nucleus

Nucleus:

The center of the atom
Contains the protons and the neutrons
Contains most of the atom’s mass

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Atomic Nucleus

Proton

Positive charge (+)
Protons are nearly 2000 times more massive as the electron
Found in nucleus

Neutron:

Found in the nucleus
No charge
Approximately same mass as proton

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Outside the Atomic Nucleus

Electrons

Surround the nucleus
Move around the nucleus
Are very small
Negative charge
Outside the nucleus of an atom is mostly empty space

Valence Electrons

The electrons in the outermost energy level (shell)
Most shells full at 8 electrons

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Elements

Any material that is made up of only one type of atom is classified as an element.

Ex. Pure gold (Au) contains only gold atoms

Ex. Nitrogen (N) gas = only nitrogen atoms

All of the elements are listed in a chart called the Periodic Table of Elements
Approx 100 elements
90 found in nature
The rest have been created in a laboratory

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Atomic Symbol

Each element is designated by its atomic symbol
Name comes from the letters of the element’s name.
1^st letter of the element is always CAPITALIZED
2^nd letter (if there is one) always lower case

Ex: C = Carbon,

Cl = Chlorine

Ex: Co = Cobalt…

…Different from CO = Carbon + Oxygen

Sometimes the name originates from the Latin name

Ex: Gold = Au for the Latin name aurum

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Atomic Number

Atomic number: number of protons in the nucleus

This DEFINES the element
If an atom is neutral, the number of protons is equal to the number of electrons
Q: If an oxygen atom has 8 electrons it will also have ____ Protons.

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Mass Number

Mass Number:

Is the total number of protons and neutrons in the nucleus
Found by rounding off the atomic mass
This is how isotopes are identified

Helium:

Mass number 4

Atomic number -2

number of neutrons 2

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Isotopes: atoms of the same element, with the same number of protons but different number of neutrons

They have different mass numbers

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Practice

If the atomic number is 9,

What is the element name?
How many protons does it have?
How many electrons does it have?

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How many protons does platinum have?
How many electrons does lead have?
How many neutrons does mercury have?
What similarities do these three elements have?�

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Day 2 notes

Types of Elements

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Early Versions of the Periodic Table

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Early Versions of the Periodic Table

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Dmitri Mendeleev

Dmitri Mendeleev developed the periodic table in 1869

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1. He grouped elements with similar chemical and physical properties together

2. He arranged the elements in increasing atomic mass.

3. He predicted the properties of elements not yet discovered.

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Mendeleev’s Periodic Table

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Periodic Table

Today’s periodic table, the elements are arranged in increasing atomic number so elements with similar properties fall in the same group.

Note: Ar and K are ordered according to atomic number, not atomic mass

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Periodic Law

Periodic Law: When elements are arranged in increasing atomic numbers, there is a repeating (periodic) pattern to the properties.

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Metals

Elements that are shiny, opaque
Good conductors of electricity and heat
malleable = can be bent without breaking
Ductile = can be drawn into wires
Most are solid at room temperature

*Mercury (Hg) is liquid at room temperature

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Nonmetals

On the right side of the periodic table
Very poor conductors of electricity and heat
Transparent
Not malleable nor ductile
Are brittle and shatter
Some are solid, liquid and gas

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Metalloids (Semiconductors)

Six elements only
Found between metals and nonmetals in the periodic table
Have both metal and nonmetal characteristics
B; Si; Ge; As; Sb;Te

(Important for electronics/microchips)

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Group (Family)

Vertical column
18 groups total
Describes properties of their elements

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Period

A Period is a horizontal row
7 periods on the table.
A Periodic trend of atom size.
Atoms get smaller from left to right on the periodic table.
Atoms get larger as you go down a group/family.

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End Day 2 notes

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Day 3 notes

Period Table Groups

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Alkali Metals

Group 1 (except Hydrogen)
Have one valence electron
Tend to lose one electron in reactions
React violently
Soft & shiny
Ex: Sodium (Na)

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Alkaline-Earth Metals

Group Two
Have two valence electrons
Tend to lose two electrons in reactions

Ex: Calcium (Ca) in bones.

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Transition Metals

Groups 3-12
Less reactive
Ex: Gold (Au)

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Inner-Transition Metals

The two rows at the bottom of the table.

-Lanthanides (top row)

-Actinides (bottom row)

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Inner Transition Metal

The inner transition metals are placed at the bottom only to save space.

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Halogens

Group 17.
Have 7 valence electrons
Tend to gain one electron in reactions

Ex: Chlorine

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Noble Gases

Group 18
Have a full valence shell with 8 electrons
Un-reactive/stable

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End Day 3 Notes

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Day 4 Notes

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Chemical and Physical Properties

Substance – matter that has uniform and unchanging composition

Ex. Pure water has the same lack of taste, color, boiling point, density, etc. It is always made up of hydrogen and oxygen
Ex. Sodium Chloride (Table Salt) is the same throughout made up of Sodium Chlorine (NaCl)

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Physical Property

Physical Property - can be observed or measured without changing the identity of the substance.

Ex. Observing and measuring the boiling point, density, color

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Physical States of Matter

Solid- definite shape and volume, particles tightly packed in fixed positions and can only vibrate.
Liquid- definite volume, indefinite shape, particles can flow past each other-fluid.
Gas- indefinite shape and volume. Particles move more rapidly with lots of space between them. Particles take up the volume and shape of the container.
Plasma – indefinite shape and volume; consists of positive and negatively charged particles at extremely high temperatures

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Illustration of 3 states of matter

Difference between gas and vapor

vapor is a gaseous state of a substance that is a solid or liquid at room temperature

Ex. Steam

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Chemical Properties

Chemical Properties- a substance’s ability to change to form new substances or ability not to.

Ex. Iron

Iron rusts when it reacts with oxygen in the air
Iron does not react with nitrogen gas in the air

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Physical Change

Physical Change – a type of change that alters the physical properties of a substance but does not change its composition.

Examples

Crumpled Aluminum Foil
Cutting Paper
Breaking a crystal
Boiling Water

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Chemical Change

Chemical Change – a process involving one or more substances changing into new substances (aka: a chemical reaction)

Some indicators of a chemical change:

Changing color (such as metal rusting)
Releasing/Absorbing heat (such as burning wood)
Producing light (fireflies)
Rotting

Note: energy is always involved in physical and chemical changes

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