Properties of Atoms and the Periodic Table

Atoms

• Unit of all matter, building blocks of elements

• Smallest piece of matter that has the properties of the element

• Make up elements, which combine to make up compounds

Elements• Elements are abbreviated in scientific

shorthand – first letter or two of element’s name

Latin Names

Element Symbol Latin nameCopper Cu cuprumGold Au aurumLead Pb plumbumMercury Hg hydrargyrumPotassium K kaliumSilver Ag argentumSodium Na natriumTin Sn stannum

OrganicElement

TraceMetal

Example

Compounds

• Def: two or more elements combined, pure substance.

Example

Example 2

Example 3

Structure of the Atom

• Nucleus:– Protons– Neutrons

• Electrons

Atomic Structure

Protons

• Much larger and heavier than electrons

• Protons have a positive charge (+)

• Located in the nucleus of the atom 

Neutrons

• Large and heavy like protons

• Neutrons have no electrical charge

• Located in the nucleus of the atom 

Electrons

• Tiny, very light particles

• Have a negative electrical charge (-)

• Move around the outside of the nucleus

Particle Symbol Charge RelativeMass

Electron e- 1- 0

Proton p+ + 1

Neutron n 0 1

Subatomic Particles

Atomic Structure10-13 cm

10-8 cm

Atom Models

• Scientist use scaled-up models to represent atoms.– Early models of atoms used a solid sphere– Current electron cloud model shows

electrons traveling in specific energy levels around a nucleus of protons and neutrons.

Early Model

Electron Cloud ModelExample 1

Electron Cloud Model: Example 2

Masses of Atoms

• (1) Atomic Mass

• (2) Isotopes

• (3) Ions

Atomic Mass

• Definition: Composed mostly of the protons and neutrons in the nucleus.

• Unit of measurement for atomic particles is atomic mass unit (amu), which is 1/12 the mass of a carbon atom.

• Atomic Number: this is also the number of protons in an atom

• Mass Number: The sum of the number of protons and neutrons in the nucleus of an atom

11

Na

Atomic Number

Symbol

Atomic Numberon the Periodic Table

11

Na

11 protons

Sodium

Proton Numberidentifies an Element

Reading Elements onthe Periodic Table

Mass number = number of protons + number of neutrons

Quick Check

A. Nitrogen

1) 5 protons 2) 7 protons 3) 14 protons

B. Sulfur

1) 32 protons 2) 16 protons 3) 6 protons

C. Barium

1) 137 protons 2) 81 protons 3) 56 protons

Calculating Subatomic Particles

16 31 65 O P Zn

8 15 30

8 p+ 15 p+ 30 p+

8 n 16 n 35 n8 e- 15 e- 30 e-

Isotopes

• Definition: Atoms of the same element with different numbers of neutrons

Isotopes

Isotopes

• Different isotopes have different properties

• The number of protons for a given atom never changes.

• The number of neutrons can change. 

• Two atoms with different numbers of neutrons are called isotopes

Isotopes of Chlorine

35Cl 37Cl17 17

chlorine - 35 chlorine - 37

Quick Check

Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms.

12C 13C 14C 6 6 6

#p _______ _______ _______

#n _______ _______ _______

#e _______ _______ _______

Answer Key

12C 13C 14C 6 6 6

#p 6 6 6

#n 6 7 8

#e 6 6 6

Quick CheckAn atom of zinc has a mass number of 65.

A. Number of protons in the zinc atom

1) 30 2) 35 3) 65

B. Number of neutrons in the zinc atom

1) 30 2) 35 3) 65

C. What is the mass number of a zinc isotope

with 37 neutrons?

1) 37 2) 65 3) 67

Ions

• An atom that carries an electrical charge is called an ion

• If the atom loses electrons, the atom becomes positively charged (because the number of positively charged protons will be more the number of electrons). Also called Cation

• If the atom gains electrons, the atom becomes negatively charged. Called Anion

Ions (continued)

• The number of protons does not change in an ion

• The number of neutrons does not change in an ions

• So, both the atomic number and the atomic mass remain the same.

This atom has lost an electron. Now it has one more proton than electron.

One more proton means one more positive charge.

This makes the total charge of the atom POSITIVE.

This atom has gained an electron. Now it has one less proton than electron.

One less proton means one less positive charge.

This makes the total charge of the atom NEGATIVE.

Ion Illustration

The Periodic Table

• Elements are organized to their properties in a chart called the Periodic Table.

• Elements are arranged in order of increasing atomic number.

• Periods – Horizontal Rows

• Groups – Vertical Columns

Groups

• Groups share similar properties

• Elements of the same group have the same number of electrons in their outermost shell (energy level).

• Energy Shells has a maximum number of electrons. Level 1: 2 e-. Level 2: 8 e-.

• Each row in the table ends when an outer energy level is filled.

Valence and Shells

Periods

• Horizontal rows of elements that contain increasing number of protons and electrons.

• Elements are classified as metals, non-metals, or metalloids.

• Elements are synthesized in laboratories all over the world.

• Notes: H and He are the building blocks of other naturally occurring elements

Trends in the Periodic Table• Metals

– Alkali Metals– Alkali Earth Metals– Transition Metals– Other (Rare) metals

• Metalloids– Semi-conductors

• Non-metals– Halogens– Other Non-metals– Noble Gas

Properties of Metals

• Conduct heat and electricity• Luster – reflect light well• Malleable – can be hammered or rolled

into sheets• Ductile – can be drawn into wire• Ionic Bonding – when combined with

non-metals• Metallic Bonding – ions are sliding layers

and electrons are weakly held

Alkali Metals

• Group 1: Soft, white, low-density, low-melting, highly reactive metallic elements

• Highly reactive with oxygen and water

• Uses:– Human Health: sodium, potassium– Photocells– Francium – a radioactive element which

breaks down giving off particles and energy

Alkali Earth Metals

• Group 2: Not found naturally in elemental form; two electrons in outer energy level. Much less reactive than Alkali Metals

• Uses:– Strontium and magnesium found in fireworks– Magnesium in vehicles, ladders and bats– Calcium in statues and countertops– Barium in disease diagnoses– Radium formerly used in cancer treatment

Transition Metals

• Group 3-12: They are characterized by multiple valences, colored compounds, and the ability to form stable complex ions.

• Often occur in nature as uncombined elements

• Uses:– Chromium – colored compounds, found in

rubies and emeralds– Iron – widely used, main ingredient in steel

Transition Metals (Continued)

• Uses:– Cobalt and nickel – used in some steels– Nickel – used to coat other metals– Copper – used in electric wiring– Silver – used in photographic film, jewelry– Gold – used in jewelry– Zinc and cadmium – used to coat and plate

other metals– Mercury – only room temperature liquid metal

Other / Rare Metals

• Any metal that is difficult to extract from ore and is rare and expensive commercially

Properties of Metalloid

• Between Metal and Non-metal

• Greek metallon = "metal“ and eidos = "sort".

• Form ionic and covalent bonds

• Have some metallic and some non-metallic properties

• Partial conduction give them “semiconductor” characteristics.

Semi-conductor

• Silicon in particular, which conducts electricity under certain conditions

• Computer chips and other electronic devices.

Properties of Non-Metals

• Usually gases or brittle solids at room temperature

• Not malleable or ductile• Poor conductors of heat and electricity• Usually not lustrous (shiny)• Form ionic bond when combined with

metals• Form covalent bond with another non-

metal

Hydrogen

• Most common element in the universe

• Diatomic molecule - H2

• Highly reactive element found mostly on Earth as part of water compound

Halogen

• Group 17: Pure halogens exist as diatomic molecules, and they are highly reactive with Alkali Metal to form salt.

• Examples: bromine, iodine, fluorine, chlorine.

• Uses:– Chlorine – disinfectant and bleach– Bromine – dyes in cosmetics– Iodine – hormone regulation, disinfectant

Noble Gas

• Group 18: They are monatomic (isolated) and chemically stable (inert). Also called inert gas.

• Uses:– Helium – used in blimps and balloons– Neon, argon, and krypton – used in lights

Atomic RadiiIncreasing Atomic Radius

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Ato

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Rad

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Atomic Radii

• Atomic Radii increase as you go down the group with increasing atomic number.

• Atomic Radii decrease as you go across the period with increasing atomic number. As proton number increases from left to right, the attraction to the nucleus becomes greater.

• Francium (Fr) is therefore the element with the largest atomic radius.