Chemistry

Grade 9 Exam

Atom

Atom

the smallest thing to exist and the building blocks for everything

Nucleus

Center of an atom, positively charged

Orbitals/Shells

Surronds the nucleus, has electrons

Electron

Sub atomic particle, negatively charged,found in the orbitals

Proton

Sub atomic particle,positively charged,found in the nucleus

Neutrons

Sub atomic particle, no charge/neutral,found in the nucleus

Metals

solid,high density/melting point,malleable/ductile,good conductors, mixes to make alloys

Non-metal

exists in all 3 states,low density/melting point,brittle,insulators

Metalloids

properties of both metals and non-metals, semi-conduction,mostly solids,lusterous

Trend of the periods

The atoms get larger because they have more orbitals

Trend of the groups

The elements become less reactive from left to right because their outer shells are almost full or full

Chemical Properties

a characteristic of a particular substance that can be observed in a chemical reaction

Physical Properties

a characteristic of matter that is not associated with a change in its chemical composition (lusterous,solid,melting point)

Ancient Philosophers

Everything in the universe is made up of elements like fire,water,earth and wind - Before 400CE

Ancient Atomists

Atomas means “not to be cut” and parmanu means invisible grain, both refer to the smallest piece of matter. Atoms are uncuttable -400CE

John Dalton

Atoms are made up of a single material that is formed into different sizes and shapes. Atoms of different elements are different- 1803

J.J Thompson

There are small, negatively charged particles inside and atom called electrons. This theory led to the “plum pudding” model, in which negatively charged particles are stuck in a positively charged substance - 1897

Ernest Rutherford

Atoms contain mostly empty space. Most of an atom’s mass is the nucleus. The nucleus is positively charged. - 1908

Niels Bohr

Electrons are scattered around the nucleus at a distance. Electrons location depends on how much energy they have. - 1913

Alkali metals

Chemical Properties - very reactive with water and air

Physical Properties - Lusterous,malleable,ductile,conducts heat/electricity

Alkali earth metals

Chemical Properties- reacts with water and air, highly reactive

Physical Properties- good conductors,lustre when cut,low melting and boiling point,malleable,ductile

Halogens

Chemical Properties- Highly reactive, all oxidize

Physical Properties - Non-metals, noticeable colour,disenfectants

Nobel Gases

Chemical Properties - not reactive,don’t form compunds

Physical Properties - colourless,odorless,tasteless,glows brightly when electric currents pass through them