Periodic table

PS.4 Periodic Table

10
Ne

Neon

20

Parts of an Element

Parts of an Atom/Element

● The tiny, central core of an atom is called the NUCLEUS.

● Inside the nucleus there are two different particles:

○ Protons: In the nucleus and have a positive charge

○ Neutrons: In the nucleus and have a neutral charge (or no charge)

● The third type of particles move in the space AROUND the nucleus

○ Electrons: Move around the atom and have a negative charge

● Atoms consist of different pieces, or parts.

Atomic Number

Atomic Number

○ How many protons and electrons are in a neutral

atom
■ The number of protons does NOT change!
■ Tells us the IDENTITY of an element.

○ REMEMBER: All atoms of a particular element

have the SAME NUMBER of protons

○ Atoms are normally NEUTRAL with the same # of

protons and Electrons

Calculating Mass Number

Mass Number (Atomic Mass)

○ Measured in Atomic Mass Units (amu)

■ Protons- 1 amu
■ Neutrons- 1 amu
■ Electrons- almost 0 amu

○ Tells us the # of neutrons that are in an atom
○ To find the number of neutrons in an atom you do the

following:
Atomic mass – protons

○ To calculate the mass number = protons + neutrons

ATOMIC MASS

● Atomic Mass is the weighted average of the masses of all the naturally occurring

isotopes of an element.

● You can calculate the average atomic mass by multiplying the mass # of each

isotope by its percentage abundance (in decimal form) and then adding these
amounts together.

Periodic Table Facts

●The periodic table of elements is a tool used to organize information about
the elements

●There are more than 110 known elements!

●No element with an atomic number greater than 92 is found naturally on
Earth
○The remaining elements are artificially produced in a laboratory setting

●An atom’s identity is directly related to its number of protons in the nucleus
(the atomic number)

●The vertical columns in the table are called groups or families

●The horizontal rows are called periods

Trends in The Periodic Table

The periodic table is divided up based on metals, non-metals, and metalloids

●Metals are located on the LEFT of the stair-step line (except Hydrogen)

●Non-metals are located on the RIGHT of the stair-step line

●Metalloids are located ON the stair-step line

Properties of metals, non-metals, metalloids

Each element has a unique set of properties and can be found on the
periodic table. Elements can be divided up into metals, nonmetals,
and metalloids.

● Metals: shiny, good conductors of thermal energy, malleable, and

ductile

● Nonmetals: dull (not shiny), poor conductors, solid nonmetals tend

to be brittle and unmalleable
Examples include: neon and carbon

● Metalloids: are also called semiconductors, have properties of

metals and nonmetals, some are shiny but others are dull, they are
somewhat malleable and ductile, some conduct thermal energy and
electrical current well.
Examples include: silicon and boron

IONS

● Although atoms are normally neutrally charged (same # of protons and electrons),

however; that’s not always the case.

● Atoms can have an unequal number of electrons and protons and when they do they

become a charged particle called an ion.

○ Ions can be positively or negatively charged.

How can you tell one isotope from

another?

MASS NUMBER!

PROTONS:
NEUTRONS:
ELECTRONS:
MASS #:

PROTONS:
NEUTRONS:
ELECTRONS:
MASS #:

Isotopes

● Each element has a limited number of isotopes that occur naturally

● An isotope is written like this:

Element Name - mass #

● Some isotopes of an element have unique properties because they

are considered to be unstable.

● An unstable atom is an atom whose nucleus can change its

composition.

● However; most isotopes have the same chemical and physical

properties.

Types of Compounds

There are millions of different ways to
classify compounds! One simple way to
classify them is by the type of bond they

contain.

Ionic Compounds

● Compounds that contain ionic bonds

○ Ionic bonds are bonds that are formed between two oppositely charged ions.

■ Electrons are transferred from the metals, which become positively charged, to the nonmetal

atoms, which become negatively charged.

■ Metals tend to LOSE electrons in chemical reactions, forming positive ions

■ Non-metals tend to gain electrons in chemical reactions, forming negative ions

○ Ionic compounds can be formed by the reaction of a metal and a nonmetal.

■ Example: SODIUM (NaCl)

Properties of Ionic Compounds

● Brittleness

○ Ionic compounds will shatter when hit with a hammer

● High melting points

○ Ionic compounds are almost always solids at room temperature. It will melt

only at temps high enough to overcome the strong ionic bonds. Sodium
chloride for instance must be heated to 801 degrees Celsius before it will melt.

● Soluble

○ many will dissolve easily in water

● Electric Conductivity

○ The solution created when an ionic compound dissolves in water can conduct

an electric current *undissolved crystals of ionic compounds will not*

Covalent Compounds

● Compounds composed of elements covalently

bonded
○ Covalent (molecular) bonds form when atoms SHARE

electrons

■ Examples: Carbon Dioxide, Water, and Sugar

Using the periodic table, what
do you notice about the above
compounds?

Properties of Covalent Compounds

● Low melting points:

○ They exist as independent particles called molecules. The

forces of attraction are much weaker than ionic bonds
therefore they have lower melting points than ionic
compounds

● Solubility:

○ Many do NOT dissolve in water. Very few do.

● Electric Conductivity:

○ Some of the covalent compounds form ions when they dissolve in water.

Solutions of these compounds, called acids, do conduct electric current.

○ However; most of the solutions from covalent compounds do not conduct

an electric current

Group Names

Valence Electrons

Group 1: Alkali Metals

1

Group 2: Alkaline Earth Metals

2

Groups 3-12: Transition Metals

1-2

Group 13: Boron Group

3

Group 14: Carbon Group

4

Group 15: Nitrogen Group

5

Group 16: Oxygen Group

6

Group 17: Halogens

7

Group 18: Noble Gases

8

Groups or Families

● The properties are similar in groups because they have the SAME # of Valence

electrons in their outermost energy level.

What is a valence electron?

How many electrons can be in each SHELL of an atom?

1st Shell- Maximum of 2
2nd Maximum of 8
3rd Shell- Maximum of 18

Group 1

● Commonly referred to as the Alkali Metals.
● The most reactive elements are in groups 1 & 2. This is because of

the number of electrons in the outermost energy level.

● They are soft enough to be cut with a knife

● The densities are so low that lithium, sodium, and potassium float on water

● They are the most reactive of the metals because their atoms can easily give

away the single electron in their outer shell or level.
○ Usually stored in oil to prevent them from reacting with water and oxygen in the atmosphere

Group 1-Properties Continued

Group 2

● Commonly referred to as the Alkaline Earth Metals.

● Very reactive but less reactive than group 1

● Silver colored but more dense than alkali metals

How many valence electrons do these elements have?

● These groups are described using one name transition metals.

● These are not as reactive as groups 1 and 2 because they do not

give away their electrons as easily.

● Their properties vary widely between each individual element.
● Shared properties include: shiny, good conductors of thermal

and electric current, higher densities and melting points
(except mercury) than groups 1 and 2

● Valence Electrons:

○ Varies among elements

Groups 3-12

Lanthanides and Actinides

Lanthanidesare called this because they follow the element lanthanide (transition metal
with atomic #57).

•Shiny, reactive metals, and some are used in different types of steel

Actinides are called this because they follow the element actinium which is (transition metal with
atomic # 89)

•All atoms of actinides are RADIOACTIVE which means they are unstable. The atoms of a
radioactive element can change into atoms of different elements.

•Elements listed after uranium (#92) do not occur in nature. They are often produced in
laboratories

Groups 13-16: Groups with Metalloids

Group 13: Boron Group

○ Valence Electrons= 3 (group

#-10)

○ Reactive

○ Solids at Room Temperature

Group 14: Carbon Group

○ Valence Electrons: 4

○ Reactivity varies among

elements

○ Solids at Room temp.

Group 15: Nitrogen Group

• Valence Electrons: 5
• Reactivity varies among elements
• All but Nitrogen are solids at room temp.

Group 16: Oxygen Group

• Valence Electrons: 6
• Reactive
• All but oxygen are solids at room temp.

Group 17: Halogens

● Only contains NONMETALS

● Valence Electrons: 7

● Reactivity: Very reactive (most reactive nonmetals)

● Other shared properties: poor conductors of electrical current, react

violently with alkali metals to form salts, never found uncombined in
nature

● NONMETALS
● Valence Electrons: 8 (except helium which has 2)
● Reactivity: unreactive because they have a

complete set of electrons in their outer level they do
not react or combine with other elements under
normal conditions

● Shared properties: colorless, odorless gases at

room temp.

● All are found in the Earth’s atmosphere in small

amounts.

● Argon is the most abundant noble gas in the

atmosphere (makes up almost 1%)

Group 18: Noble Gases

What about Hydrogen?

● Hydrogen stands apart from all other elements because its

properties do not match the properties of any single group.

● It is above Group 1 because it has 1 valence electron in its

outermost level. What does that tell us about its reactivity?

● However; it’s physical properties are more like nonmetals

than metals

● Hydrogen is the most abundant element in the universe and

its reactive nature makes it useful as a fuel in rockets.

● Other properties: colorless, odorless gas at room temp., low

density, reacts explosively with oxygen