Chemistry

Question 1

What are atoms?

Answer 1

The basic units of matter made up of protons, neutrons, and electrons.

Question 2

What is the nucleus of an atom?

Answer 2

The dense center of an atom containing protons and neutrons.

Question 3

What are electrons and where are they found?

Answer 3

Negatively charged particles found in shells (energy levels) around the nucleus.

Question 4

What defines an element?

Answer 4

A substance made of only one type of atom, with a specific number of protons.

Question 5

How are elements represented?

Answer 5

By chemical symbols, e.g., H for hydrogen and O for oxygen.

Question 6

What is a compound?

Answer 6

A substance formed when two or more elements chemically bond.

Question 7

How do compounds differ from mixtures?

Answer 7

Compounds have fixed ratios and are chemically bonded, while mixtures are physically combined.

Question 8

What is a reactant in a chemical reaction?

Answer 8

A substance present at the start of a reaction.

Question 9

What is the product in a chemical reaction?

Answer 9

The substance formed after the reaction.

Question 10

What was Dalton’s atomic theory?

Answer 10

All matter is made of indivisible atoms, which combine in fixed ratios.

Question 11

What did J.J. Thomson discover?

Answer 11

The electron, leading to the plum pudding model of the atom.

Question 12

What was Rutherford’s gold foil experiment?

Answer 12

It showed atoms have a dense, positive nucleus surrounded by empty space.

Question 13

How did Bohr improve the atomic model?

Answer 13

He proposed electrons orbit the nucleus in fixed energy levels.

Question 14

How did Mendeleev organize the periodic table?

Answer 14

By increasing atomic mass and grouping elements by similar properties.

Question 15

What key change occurred in the modern periodic table?

Answer 15

It is organized by atomic number, not mass.

Question 16

What are groups in the periodic table?

Answer 16

Vertical columns that contain elements with similar chemical properties.

Question 17

What are periods?

Answer 17

Horizontal rows that show elements with the same number of electron shells.

Question 18

What trend occurs across a period?

Answer 18

Atomic size decreases, and elements become less metallic.

Question 19

What are properties of metals?

Answer 19

Conduct electricity, malleable, ductile, shiny, and high melting points.

Question 20

What are properties of non-metals?

Answer 20

Poor conductors, brittle, dull, and low melting points.

Question 21

Why are Group 1 metals so reactive?

Answer 21

They have one electron in their outer shell, which is easily lost.

Question 22

What happens when alkali metals react with water?

Answer 22

They produce hydrogen gas and an alkaline solution.

Question 23

How does reactivity change down Group 1?

Answer 23

Reactivity increases because the outer electron is farther from the nucleus.

Question 24

What are the states of halogens at room temperature?

Answer 24

Fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid.

Question 25

What is displacement in halogens?

Answer 25

A more reactive halogen displaces a less reactive halogen from its compounds.

Question 26

How does reactivity change down Group 7?

Answer 26

Reactivity decreases as it is harder to attract electrons.

Question 27

Why are noble gases unreactive?

Answer 27

They have full outer electron shells.

Question 28

How do boiling points change down Group 0?

Answer 28

Boiling points increase due to stronger intermolecular forces.

Question 29

What is an ion?

Answer 29

An atom or group of atoms with a positive or negative charge.

Question 30

How do metals form ions?

Answer 30

By losing electrons to form positive ions (cations).

Question 31

How do non-metals form ions?

Answer 31

By gaining electrons to form negative ions (anions).

Question 32

What is ionic bonding?

Answer 32

The transfer of electrons between a metal and a non-metal.

Question 33

What holds ionic compounds together?

Answer 33

Strong electrostatic forces between oppositely charged ions.

Question 34

What are properties of ionic compounds?

Answer 34

High melting points, soluble in water, and conduct electricity when molten or dissolved.

Question 35

What is covalent bonding?

Answer 35

The sharing of electrons between two non-metals.

Question 36

What is a single covalent bond?

Answer 36

One pair of shared electrons.

Question 37

What are simple molecular substances?

Answer 37

Small molecules with strong covalent bonds but weak intermolecular forces.

Question 38

Why do simple molecular substances have low boiling points?

Answer 38

Weak intermolecular forces require little energy to overcome.

Question 39

What are examples of giant covalent structures?

Answer 39

Diamond, graphite, and silicon dioxide.

Question 40

Why is diamond hard?

Answer 40

Each carbon atom forms four strong covalent bonds.

Question 41

Why does graphite conduct electricity?

Answer 41

It has delocalized electrons between its layers.

Question 42

Why does reactivity increase down Group 1?

Answer 42

The outer electron is farther from the nucleus, making it easier to lose.

Question 43

Why does reactivity decrease down Group 7?

Answer 43

Attracting an extra electron becomes harder due to increased shielding.

Question 44

Why do noble gases have higher boiling points as you go down the group?

Answer 44

Larger atoms have stronger intermolecular forces.

Question 45

What is the significance of the periodic table's organization?

Answer 45

It predicts element properties and reactions.

Question 46

How does atomic size change across a period?

Answer 46

It decreases due to increased nuclear charge pulling electrons closer.

Question 47

What are alloys and why are they useful?

Answer 47

Mixtures of metals to improve strength, corrosion resistance, or other properties.