Chapter 2- Atoms, elements and compounds

Atoms

the Smallest unit of a matter 🔬

Elements

Pure substance that cannot be further seperated by chemical means and made of particles with the same number of protons

Compounds

A substance that are made of 2 or more substances chemically bonded together 🔗 in a fixed proportion

Mixture

Two or more substances that are mixed together but are not chemically bonded could be separated by physical means 🥗

Atomic Structure (from image)

Atoms consist of a central nucleus containing positively charged protons and neutral neutrons, surrounded by negatively charged electrons orbiting in shells. ⭕

Isotopes

different atoms of an element with different mass number and neutrons in the nucleus but the same number of proton and electrons meaning the same chemical properties ⚖️

Isotopes (Chemical Properties)

Isotopes have the same number of valence electrons so all isotopes have the same chemical properties 🧪

Isotopes (Physical Properties)

The difference between isotopes is the neutrons which are neutral particles within the nucleus and add mass only The difference in mass affects the physical properties, such as density, boiling point and melting point 🌡️,

Ionic Bond

is a strong electrostatic attraction between oppositely charged ions & between metal and non metal 🧲

IONS

Ions are charged particles mad from an atom, or group of atms, by Loss or gain of electrons ➕➖

Valency

The number of elctron its atom lose, gain or shares, to form a compound 🤝

Valency Rules

Metal = # Group, Non - metal = 8 - Group # 🔢

Compound ions

Some covalent compounds have charge -> Compound ions ⚛️

Ionic groups made with covalent bonds (Polyatomic ions definition)

Ions that are made up of two or more atoms joined together by covalent bonds, but which have an overall electrical charge

Properties of Ionic compound (Physical)

Ionic compounds are solid at R.T.P, They form lattice structure, High M.P & High B.P Held by the strong electrostatic force of attraction with a regular lattice arrangement of alternating positive and negative ions, Soluble in water -> Good electrical conductivity when aqueous/molten & poor conductivity as a sold 🧊

Covalent bonds

formed when a pair of electrons is shared between two atoms leading to a noble gas/ octet formation & Between nonmetals and non metal ☁️

Properties of Covalent compound (Physical)

liquid or gas at RTP, Formed of simple molecules and atoms joined together by covalent bonds, low M.P & B.P -> Not much energy is needed to break the weak intermolecular force, Covalent compounds have no ions present to carry current therefore do not conduct electricty 💧

Simple molecular substance

Consist of simple molecules with weak intermolecular force holding to each other 🫧

Giant Structures

Macromolecules, Ionic Lattices, Metallic lattices simpply put are compound with large structure and strong bons between each molecules 🏗️

Diamond 💎 (Structure)

Diamond are made of carbon atoms, Each carbon mol. Is bond with 4 others, Tetrahedral structure 💎

Diamond 💎 (Properties)

Non metallic -> Do no conduct electricity, Use as jewellry -> as it is colouless shape which is transparent crystals, Drill bits -> hardest natural substance on earth ⛏️

Graphite ✏️ (Structure)

In graphite is is formed in hexagonal shape in each layer with strong covalent bonds in each layer, Each carbon atom formed a triple bond with one free electron 📝

Graphite ✏️ (Properties)

Conduct electricity, Soft, slippery -> lubricants ⚙️

Metallic Bond

The electrostatic attraction between the positive ions in a giant metallic lattice and the "sea" delocalised electron 🌊

Metallic Bond Structure (Image Description)

A regular arrangement (giant lattice) of closely packed positive metal ions surrounded by a "sea" of freely moving, delocalized electrons that can move between the ions. 🔋

Properties of Metals

Conduct electricity -> Free electrons can carry current, Malleble -> easily bent and shaped, slide on each other to form new bond when bent, Ductile 🔨