TH REAL SCI TOPIC TEST TERM 1

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Rutherford's Atomic Model

Everything around us is made up of very tiny particles called atoms.

Definition of an Atom

Smallest building block of matter.

Energy Shells and Energy Levels

As energy shells move away from the nucleus, their energy level increases.

Valence Shell

The last energy shell, furthest from the nucleus.

Valence Electrons

Electrons located in the valence shell.

Element

Substance with the same type of atom.

Example of Elements

Sodium element only contains sodium atoms, Chlorine element only contains chlorine atoms.

Difference Between Chlorine and Sodium Atom

Different number of protons, electrons, and neutrons.

Atomic Number

Number of protons in an atom.

Electrical Neutrality in Atoms

Number of electrons is always equal to the number of protons, making the net charge zero.

Charge of Proton

+1

Charge of Electron

-1

Mass Number

Sum of the number of protons and neutrons.

Example: Sodium

Mass number = 23, Atomic number = 11, Protons = 11, Neutrons = 12.

Periodic Table

A table arranging elements based on increasing atomic number.

Electron Arrangement

Electrons are located in energy shells, with specific maximum capacities.

First Shell Capacity

2 electrons.

Other Shells Capacity

8 electrons.

Electron Configuration Rule

2,8,8

Example: Sodium Configuration

2,8,1

Valence Electrons and Group Number

Number of valence electrons determines the group number.

Number of Shells and Period Number

Number of shells used determines the period number.

Example: Sodium Group and Period

3 shells, 1 valence electron → Group 1, Period 3.

Example: Chlorine Group and Period

3 shells, 7 valence electrons → Group 17, Period 3.

Ion Formation

Atoms gain or lose electrons to become stable.

Example: Sulfur Ion

Sulfur gains 2 electrons to become sulfide ion (S²⁻).

Example: Magnesium Ion

Magnesium loses 2 electrons to form Mg²⁺ ion.

Ionic Bonding

Formed between cations and anions due to opposite charges.

Example: Sodium and Oxygen

Sodium donates electrons to oxygen, forming Na₂O.

Elements, Compounds, and Mixtures

Different ways atoms combine in substances.

Example of Chemical Formulas

H₂O (Water), CO₂ (Carbon dioxide), C₆H₁₂O₆ (Glucose).

Physical vs Chemical Changes

Physical: No new substances, reversible. Chemical: New substances, irreversible.

Example of Physical Change

Dissolving sugar in water, glass breaking.

Example of Chemical Change

Burning wood, rust formation.

Word Equation for Rust Formation

Oxygen + Water + Iron → Rust.

Chemical Reaction Process

Reactants undergo bond breaking and reforming to produce products.

Signs of a Chemical Reaction

Temperature change, color change, gas formation, precipitate formation, smell change.

Acids and Bases

Acids release H⁺ ions, bases release OH⁻ ions.

Testing for Acids and Bases

Using litmus paper.

pH Scale

Measures acidity or alkalinity of a substance.

Litmus Paper Test for Acids

Red litmus stays red, blue litmus turns red.

Litmus Paper Test for Bases

Blue litmus stays blue, red litmus turns blue.

Litmus Paper Test for Neutral

No color change in either red or blue litmus.

Atom

Smallest building blocks of matter; contains protons, electrons, and neutrons.

Proton

Positively charged particle found in the nucleus of an atom.

Neutron

Particle with no charge found in the nucleus of an atom.

Electron

Negatively charged particle that orbits the nucleus in energy levels.

Cation

Positively charged ion formed by losing electrons.

Anion

Negatively charged ion formed by gaining electrons.

Ionic Bond

The electrostatic attraction between oppositely charged ions.

Chemical Reaction

A process that leads to the transformation of one set of chemical substances to another.

Reactants

Substances that undergo a chemical change in a reaction.

Products

Substances formed as a result of a chemical reaction.

Acid

A substance that releases hydrogen ions (H⁺) in water.

Base

A substance that releases hydroxide ions (OH⁻) in water.

pH Scale

A scale to measure the acidity or alkalinity of a solution.

Electrons in Valence Shell

These determine the group number of an element on the periodic table.

Electron Configuration

The distribution of electrons in an atom's energy levels.