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Sub-Atomic Particles of an Atom Electron - Negatively charged particle present outside the nucleus of an atom. Proton - Protons are positively charged and are present inside the nucleus. Neutron - Neutrons are neutrally charged particles, present within the nucleus of an atom.

Know the subatomic particles and their charges

Each shell can contain only a fixed number of electrons: The first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on.

Know the number of electrons in the first 3 shells

In chemistry and physics, a valence electron is an outer shell electron that is associated with an atom, and that can participate in the formation of a chemical bond if the outer shell is not closed

Valence shell/electrons

An electron cloud is the region of negative charge surrounding an atomic nucleus that is associated with an atomic orbital. It is defined mathematically, describing a region with a high probability of containing electrons.

Describe electron clouds

A metal made by combining two or more metallic elements, especially to give greater strength or resistance to corrosion.

Alloy

Including examples each of two or more different physical forms in which an element can exist. Graphite, charcoal, and diamond are all allotropes of carbon.

Define allotrope

A metalloid is a type of chemical element which has properties in between, or that are a mixture of, those of metals and non-metals. E.g. Boron Silicon Germanium

Metalloids

• Annealing - is a heat process whereby a metal is heated to a specific temperature /colour and then allowed to cool slowly. This softens the metal which means it can be cut and shaped more easily.

Annealing

Quenching can be described as an operation that provides for the rapid cooling of steel from a high temperature. If rapid enough, will usually result in the steels becoming much harder and stronger than if it had been allowed to cool more slowly.

Quenching

Tempering is a heat treatment technique applied to ferrous alloys, to achieve greater toughness by decreasing the hardness of the alloy. The reduction in hardness is usually accompanied by an increase in ductility, thereby decreasing the brittleness of the metal.

Tempering

These steels are the most common. characteristic combination of weldability and formability. They cannot be hardened by heat treatment but have the useful property of being able to be work hardened to high strength levels whilst retaining a useful level of ductility and toughness. Standard austenitic steels are vulnerable to stress corrosion cracking. They are nominally non-magnetic

Austenitic steel

Allows them to be hardened and tempered much like carbon and low-alloy steels. They are used where high strength and moderate corrosion resistance is required. They are more common in long products than in sheet and plate form. They have generally low weldability and formability. They are magnetic.

Martensitic steel

Metallic bond, force that holds atoms together in a metallic substance. As a consequence, the valence electrons continually move from one atom to another and are not associated with any specific pair of atoms. In short, the valence electrons in metals, unlike those in covalently bonded substances, are nonlocalized, capable of wandering relatively freely throughout the entire crystal.

Metallic Bonding

The key difference between anion and cation is that anions are the negatively charged ions formed from neutral atoms whereas cations are positively charged ions formed from neutral atoms. Both attract to form compounds

Define anion and cation

When an element composed of atoms that readily lose electrons (a metal) reacts with an element composed of atoms that readily gain electrons (a nonmetal), a transfer of electrons usually occurs, producing ions. The compound formed by this transfer is stabilized by the electrostatic attractions (ionic bonds) between the ions of opposite charge present in the compound.

Define ionic compounds and write formula for them

Ionic bonding is a type of chemical bonding that involves the electrostatic attraction between oppositely charged ions, and is the primary interaction occurring in ionic compounds.

Ionic bonding

Consequently, ionic solids do not conduct electricity. When dissolved in water, the ionic bond is broken, which allows the charged ions to be separated and flow freely. The water provides the movement of particles and the separated ions provide the conductivity. Since both are present, an electrical current is created to conduct electricity.

Ions in solution

The Law of Conservation of Mass (or Matter) in a chemical reaction can be stated thus: In a chemical reaction, matter is neither created nor destroyed.

Law of Conservation of Matter

A chemical reaction is connected with - Change of temperature - the mixture cools down or heats up. - Change of colour yellow product - Emission of gas - Forming of precipitates

Describe what a chemical reaction is

Acids: taste sour, corrosive, release H+ in water, neutralize bases Bases: taste bitter, slippery, release OH- in water, neutralize acid

Acids and Bases

The pH scale is a measure of how acidic or basic a liquid substance is. red is acidic, blue is basic, green is neutral

PH scale

Strong acids completely dissociate in water, forming H+ and an anion. Strong bases dissociate 100 percent into the cation and OH- (hydroxide ion) A weak acid only partially dissociates in water to give H+ and the anion. Like weak acids, weak bases do not completely dissociate in aqueous solution.

Strengths of acids and bases

Radioactive atoms are unbalanced that strive for stability, by emitting energy (radiation).

Radioactive Decay

An alpha particle is identical to that of a helium nucleus It contains two protons and two neutrons

Alpha Decay

A beta particle is a fast-moving electron which is emitted from the nucleus of an atom undergoing radioactive decay. Beta decay occurs when a neutron changes into a proton and an electron.

Beta Decay

Gamma rays are not charged particles like alpha and beta particles. Gamma rays are electromagnetic radiation with high frequency

Gamma Decay

Nuclear transmutation is the conversion of one chemical element or an isotope into another chemical element. Because any element (or isotope of one) is defined by its number of protons. A transmutation can be achieved either by nuclear reactions or by radioactive decay, where no one outside cause is needed.

Transmutation

Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons but different numbers of neutrons in each atom.

Isotopes

A radioisotope consists of unstable atoms that undergo radioactive decay emitting alpha, beta or gamma radiation.

Radioisotope

The amount of time it takes half the nuclei to decay Nuclei decay spontaneously and at random Instead we use half-life, time it takes half unstable nuclei to decay

Half Life

Alpha is stopped by paper beta is stopped by aluminium gamma is stopped by concrete

Radiation Penetration

Number is at the top, proton count symbol in the middle mass at the bottom (protons + neutrons)

Atomic number, symbol and mass

Metals (middle to left) Metalloids (half metals) staircase between metals and non-metals Non metals (upper right)

Location of metals and non metals on periodic table

Lustrous conductors malleable (hammered, pressed and not break) ductile (drawn into thin wires) sonorous (ringing sound)

Metal properties

Dull poor conductors brittle not sonorous

Non Metal

Citrus fruit tea vinegar soda

Examples of Acids

Baking Soda bleach soap

Bases examples

The branch of engineering that deals with things smaller than 100 nanometers (especially with the manipulation of individual molecules)

Nanotechnology

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