Chemistry Unit 2 Test - Electrons and Periodic Table

Q: What does the periodic table organize elements by?

A: Atomic number (number of protons).

What are the rows on the periodic table called ?

Periods

What are the columns on the periodic table called?

Groups or families

Why do elements in the same group have similar properties ?

Because they have the same valence (outer) electrons

For metals, how does reactivity change down a group? vvv

Reactivity increases as you go down a group.vvv

For metals, how does reactivity change across a period (right to left)”? ««

Reactivity decreases as you move across a period (row).

For nonmetals, how does reactivity change down a group? VVV

Reactivity decreases as you go down a group.

For nonmetals, how does reactivity change across a period (left to right)?»»

Reactivity increases as you move across a period.

What determines how reactive an element is?Explain

Reactivity depends on how easily atoms lose, gain, or share electrons to form stable compounds.

Explaination:

• Atoms want to have a full outer shell of electrons (like noble gases).

• Some atoms lose electrons to achieve this (metals).

• Others gain electrons to achieve this (nonmetals).

• How easily they can do this determines how reactive they are.

Why are metals more reactive when it’s easier to lose electrons?

Because they form positive ions more easily.

Why are nonmetals more reactive when it’s easier to gain electrons?

Because they form negative ions more easily.

What group contains the most reactive metals?

Group 1 – the Alkali Metals

What group contains the most reactive nonmetals?

Group 17 – the Halogens

Q: What does conductivity mean?

A: How well a material allows heat or electricity to pass through it.

What does malleable mean?

Able to be hammered or rolled into thin sheets without breaking.

What does ductile mean?

Can be stretched into thin wires.

Whats does brittle mean?

Easily broken or shattered instead of bending

properties of metals 

1. Malleable – Can be hammered or rolled into thin sheets.

2. Ductile – Can be drawn into wires.

3. Conductive – Good conductors of heat and electricity.

4. Shiny/Lustrous – Have a metallic sheen, especially when freshly cut.

5. Dense – Most metals have high density.

6. Solid at room temperature – Except mercury (Hg).

7. Hard and strong – Generally strong, though some (like sodium) are soft.

8. Tendency to lose electrons – Metals form cations (positive ions) in reactions.

properties of nonmetals 

• Brittle – Break easily, not malleable or ductile.

• Dull – Not shiny like metals.

• Poor conductors – Don’t conduct heat or electricity well (except graphite).

• Low density – Usually lighter than metals.

• Gain electrons easily – Form anions (negative ions).

• React with metals – Often form salts.

• Nonmetal oxides are acidic – e.g., CO₂, SO₂.

properties of metalloids

1. Semi-conductors – Conduct electricity sometimes, depending on conditions.

2. Can be shiny or dull – Often metallic-looking but not always shiny.

3. Brittle – Break easily like nonmetals.

4. Reactivity varies – Can behave like metals or nonmetals in reactions.

5. Intermediate properties – Mix of metal and nonmetal characteristics.

alkali metals 

soft, shiny, and super reactive with water.

group: 1 

• soft

• shiny, metallic 

• low density 

• very reactive (with water) 

alkaline earth metals

metallic, a bit harder, react with water less violently than alkali metals.

1. Physical Properties

   • Soft (can cut with a knife)

   • Shiny, metallic

   • Low density (some float on water)

2. Chemical Properties

   • Very reactive, especially with water → forms alkaline (basic) solutions + hydrogen gas

   • Reactivity increases down the group (Li < Na < K < …)

   • Form +1 ions (lose one electron easily)

transition metals 

strong, shiny, can have many ions, often colorful compounds.

• Hard and strong

• Shiny (metallic luster)

• High melting and boiling points

• Good conductors of heat and electricity

• Malleable and ductile

• Can form different ions (variable oxidation states)

• Often form colored compounds

• Less reactive than alkali and alkaline earth metals

• Can act as catalysts in reactions

inner transition metals

the “hidden metals” at the bottom, shiny, metallic, often high-tech or radioactive.

halogens 

highly reactive nonmetals that love to steal an electron.

• Nonmetals (except Astatine, which is metalloid)

• Poor conductors of heat and electricity

• Exist in all three states at room temperature

• Very reactive (especially with alkali and alkaline earth metals)

• Reactivity decreases down the group (F > Cl > Br > I > At)

• Form -1 ions (gain one electron easily)

noble/inert gases

“happy gases” → full outer shell, don’t want to react.

• Colorless, odorless gases

• Very low reactivity

• Poor conductors of heat and electricity

• Exist as single atoms (monatomic)

• Very stable → almost never react with other elements

• Complete outer electron shell → don’t form ions easily

What are valence electrons?

Electrons in the outermost energy level of an atom that determine chemical reactivity.

How do you determine the number of valence electrons for main-group elements?

By the group number (1–2 = same as group, 13–18 = group number minus 10).

Why are valence electrons important?

They are involved in chemical bonding (forming ions or covalent bonds).

What is the electromagnetic (EM) spectrum?

All types of electromagnetic radiation, arranged by wavelength or frequency

What is wavelength?

The distance between two consecutive peaks of a wave (measured in meters, nm).

What is frequency?

The number of wave peaks that pass a point per second (measured in Hz).

How are wavelength and frequency related?

They are inversely proportional: shorter wavelength → higher frequency.

Name the main types of electromagnetic radiation from longest wavelength to shortest.

Radio → Microwaves → Infrared → Visible light → Ultraviolet → X-rays → Gamma rays.

What are the colors of visible light from longest to shortest wavelength?

Red → Orange → Yellow → Green → Blue → Indigo → Violet (ROYGBIV).

What is a line emission spectrum?

A set of specific wavelengths of light emitted by electrons of an atom as they return to lower energy levels.

Why does each element have a unique line emission spectrum?

Because each element has a unique electron configuration and energy differences between levels.