Aadi's NS Notes

Atoms and Compounds

Atoms:

The smallest unit of an element that retains the properties of that element.
Consist of protons (positively charged), neutrons (neutral), and electrons (negatively charged).
The nucleus is made up of protons and neutrons, with electrons orbiting the nucleus.

Compounds:

Substances formed when two or more different types of atoms bond together.
Can be broken down into simpler substances by chemical means.
Example: Water (H₂O) is a compound made of hydrogen and oxygen.

Chemical Reactions and Equations

Chemical Reactions:

Processes in which substances (reactants) change into new substances (products).
Indicators of a chemical reaction include color change, temperature change, gas production, and precipitate formation.

Chemical Equations:

Representations of chemical reactions using symbols and formulas.
Reactants are shown on the left side, and products are on the right side, separated by an arrow (→).

Balancing Chemical Equations:

Ensures the law of conservation of mass is followed (mass of reactants = mass of products).
Each element must have the same number of atoms on both sides of the equation.

Steps to Balance Equations:

Write the unbalanced equation.
Count the atoms of each element in the reactants and products.
Use coefficients to balance the atoms, starting with the most complex molecule.
Check that all elements are balanced.
Ensure all coefficients are in the simplest ratio.

Reaction of Metals with Oxygen

Metals react with oxygen to form metal oxides.

General equation: Metal + Oxygen → Metal Oxide

Examples:

2Mg + O₂ → 2MgO (Magnesium reacts with oxygen to form magnesium oxide)
4Fe + 3O₂ → 2Fe₂O₃ (Iron reacts with oxygen to form iron(III) oxide, also known as rust)

pH, Acids, and Bases

pH Scale:

The ph is a number from a scale of 0-14 that indicates how much acid or base properties a substance has.

A acid has a ph lower than 7.
A base has a ph greater than 7
A netural substance has a ph equal to 7.
Measures the acidity or alkalinity of a solution.

Acids:

Substances that release hydrogen ions (H⁺) in solution.
Example: Hydrochloric acid (HCl)
They taste sour.
They are corrossive(They eat away other substances).
They can be classified as household acids(sour milk).
They can change the colour of other substances .
They are solouble in water.
They can neturalise a base.
pH Level: Acids have a pH level Less than 7. The pH scale ranges from 0 to 14, with 7 being neutral (pure water). The lower the pH, the stronger the acid.
The tempture of an acid soloution rises sharply during diluting(make (a liquid) thinner or weaker by adding water or another solvent to it.)
When diluting very strong acids can cause temptures to rise rapidly making them splash out and can even crack the glass of the container.

Bases:

Substances that release hydroxide ions (OH^-) in solution.
Have a bitter taste and slippery feel.
Example: Sodium hydroxide (NaOH)
Bases can be either water soluble or insoluble.
Bases often have a bitter taste and a slippery feel.
pH Level: Bases have a pH level greater than 7. The pH scale ranges from 0 to 14, with 7 being neutral (pure water). The higher the pH, the stronger the base.
Concentrated bases are corrosive.
All metal hydroxide , metal oxides and metal cyanates are bases.
They can neturalise an acid.

Neutralization Reactions:

Occur when an acid reacts with a base to produce a salt and water.
General equation: Acid + Base → Salt + Water

Example:

HCl + NaOH → NaCl + H₂O (Hydrochloric acid reacts with sodium hydroxide to produce sodium chloride and water)

Diatomic Elements

Diatomic elements are molecules composed of only two atoms, of either the same or different chemical elements. In the context of the periodic table, there are seven elements that naturally form diatomic molecules under standard conditions. These elements are:

Hydrogen (H₎
Nitrogen (N₂)
Oxygen (O₂)
Fluorine (F₂)
Chlorine (Cl₂)
Bromine (Br₂)
Iodine (I₂)

A common mnemonic to remember these elements is "Have No Fear Of Ice Cold Beer" where each first letter represents a diatomic element (H, N, F, O, I, Cl, Br).

Properties of Diatomic Elements:

Hydrogen (H₂)

The lightest and most abundant element in the universe.
Exists as a colorless, odorless gas.
Highly flammable and used in various industrial processes, including hydrogenation and as a fuel source.

Nitrogen (N₂)

Makes up about 78% of the Earth's atmosphere.
Colorless, odorless gas.
Inert and used to create inert atmospheres for chemical reactions and as a cryogenic agent.

Oxygen (O₂)

Essential for respiration in most living organisms.
Makes up about 21% of the Earth's atmosphere.
Supports combustion and is used in medical applications and industrial processes.

Fluorine (F₂)

Pale yellow gas.
Highly reactive and the most electronegative element.
Used in the production of fluorinated compounds, such as Teflon.

Chlorine (Cl₂)

Greenish-yellow gas.
Highly reactive and used in water purification, disinfectants, and the production of PVC (polyvinyl chloride).

Bromine (Br₂)

Red-brown liquid at room temperature.
Less reactive than chlorine but more reactive than iodine.
Used in flame retardants and certain types of photographic chemicals.

Iodine (I₂)

Shiny, black-purple solid that sublimates to a violet gas.
Essential nutrient in the human diet (as iodized salt).
Used in antiseptics and iodized compounds.

These elements exhibit diatomic behavior due to the stability provided by forming a molecule of two atoms, particularly important for elements like oxygen and nitrogen, which form strong double and triple bonds, respectively.

Elements and Atoms

An element is a basic building block of matter. It can't be broken down into simpler substances by chemical means.

Elements are made of tiny particles called atoms. All the atoms in an element are the same type, but elements can combine to form all sorts of matter, from water to diamond to you and me!

There are 118 known elements, and they're listed in a chart called the periodic table

Chemical equations

In a chemical equation, reactants are typically written on the left side, separated by plus signs (+), and products are written on the right side, also separated by plus signs. Arrows (usually pointing from left to right) indicate the direction of the reaction.

For example, the chemical equation for the combustion of methane (CH4) in oxygen (O2) to produce carbon dioxide (CO2) and water (H2O) can be represented as:

CH4 + 2O2 → CO2 + 2H2O

This equation indicates that one molecule of methane reacts with two molecules of oxygen to produce one molecule of carbon dioxide and two molecules of water. The numbers in front of the formulas (coefficients) represent the stoichiometry of the reaction, indicating the relative amounts of each substance involved.

Corrosion

Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment.
examples include the 2 types:

Acidic oxide: oxides are oxides of nonmetals. example : SO2,CO2,SO3.
Basic oxides: These are oxides of metals CaO,MgO,Na2O.

Rust

Rust typically refers to iron oxide, a compound formed when iron reacts with oxygen in the presence of water or moisture. Rusting is a form of corrosion that occurs when iron undergoes oxidation, losing electrons to oxygen atoms in the air or water.
it can be prevented by:

Oiling and Painting
Galvanizing
Electroplating

Formulas

acid + base → salt + water
acid + metal oxide → salt + water
acid + metal carbonate → salt + water + carbon dioxide
metal oxide + water → metal hydroxide
acid + metal hydroxide → salt + water
acid + metal → salt + hydrogen
non-metal oxide + water → non-metal oxide
metal + water → metal oxide

Indicators

These are chemical substances that change colour when they react with a acid or a base that dissolves in water. The colour changes depends on whether the substance is a Base or Acid.
Here is a table to show what colour it changes to when its touching a Acid or Base:

Number on ph scale	Acid or Base	Colour
1	Strong acid	Red
2	Strong acid
3	Strong acid
4	Weak acid	Orange or Yellow
5	Weak acid
6	Weak acid
7	Neutral	Green
8	Weak base	Blue
9	Weak base
10	Weak base
11	Strong base	Violet or Indigo
12	Strong base
13	Strong base
14	Strong base

Common Groups of Compounds

Compound	Name
OH	Hydroxide
NO₃	Nitrate
CO₃	Carbonate
PO₄	Phosphate
SO₄	Sulfate
SO₃	Sulfite

Common Compounds and their formulas and common names

Formula	Chemical Name	Common Name
CH₃COOH	Ethanoic acid	Vinegar
H₃PO₄	Hydrogen phosphate	Phosphoric acid
HCℓ	Hydrogen chloride	Hydrochloric Acid
HNO	Hydrogen nitrate	Nitric acid
H₂SO₄	Hydrogen sulfate	Battery Acid
H₂O	Hydrogen oxide	Water
NH₃	Hydrogen nitride	Ammonia
HCO	Hydrogen carbonate	Carbonic acid
NaC	Sodium Chloride	Table salt
NaHCO₃	Sodium bicarbonate	Bicarbonate of Soda
Na₂CO₃	Sodium carbonate	Washing Soda
KNO₃	Potassium nitrate	Saltpetre
CaCO₃	Calcium Carbonate	Marble
CaSO₄	Calcium sulfate	Plaster of Paris
CO₂	Carbon dioxide	Carbonic acid gas
MgSO₄	Magnesium sulfate	Epsom salt
CH₄	Methane	Natural Gas
CuSO₄	Copper sulfate	Blue Vitriol
KOH	Potassium hydroxide	Caustic potash
NaOH	Sodium hydroxide	Caustic Soda
Ca(OH)₂	Calcium hydroxide	Slaked lime

How to read an element on a periodic table

Element Information

Order:The order always goes from the lightest to the heaviest element
Element Symbol: This is a one- or two-letter abbreviation of the element's name (e.g., H for Hydrogen, O for Oxygen).
Atomic Number: This is the number usually located at the top of the element's box. It represents the number of protons in the nucleus of an atom of the element (e.g., Hydrogen's atomic number is 1).
Element Name: The full name of the element (e.g., Hydrogen, Oxygen).
Atomic Mass: Usually located beneath the element symbol, this number represents the average mass of the element's atoms, taking into account the relative abundance of different isotopes (e.g., Carbon has an atomic mass of about 12.01).
Electron Configuration: Sometimes included on more detailed tables, this shows the distribution of electrons in an atom's electron shells.
Atomic mass = atomic number(protons) + neutrons
Neutrons = atomic number(protons) - atomic mass
Note:When elements are written the element with the most protons are ALWAYS written First
Group and Period:
- Groups (Columns): Elements in the same column (group) have similar chemical properties because they have the same number of electrons in their outer shell. Groups are numbered from 1 to 18.
- Periods (Rows): Elements in the same row (period) have the same number of electron shells. Periods are numbered from 1 to 7.

Additional Information

State of Matter: Indicated by color-coding the element's box to show if the element is solid, liquid, or gas at room temperature.
Electronegativity: A measure of an atom's ability to attract and bond with electrons.
Density: Often included for quick reference.
Melting and Boiling Points: Important physical properties listed for some elements.

Color-Coding and Other Features

Metals, Nonmetals, and Metalloids: Some tables use color-coding to differentiate between metals, nonmetals, and metalloids.
Natural and Synthetic Elements: Some tables indicate which elements are naturally occurring and which are synthetic.