Atoms And Ions c3t28

Structure of the atom • Nobel prize Chemistry 1908 • Atomic model 1911 • First person to transmute Nitrogen to oxygen 1919 • $100 note

ATOMS Atoms are the building blocks of all matter. An atom is made up of smaller bits called… Name Protons

Charge

Position

Mass

+ve

Nucleus

1

Electrons

-ve

Outside

0

Neutrons

neutral

Nucleus

1

ELEMENTS An element is a substance made up of only 1 type of atom. There are about 112 different atom types therefore there are 112 elements. These are shown on the periodic table of the elements. On the periodic table each atom type has its information. For example… Atomic no. Symbol Name Mass no.

PERIODIC TABLE Atomic no.

Any atom can be identified by the atomic no., the symbol or by the name. For instance...

Name

Symbol Name

Symbol

Atomic No.

Hydrogen

H

1

Iron

Fe

26

Magnesium

Mg

12

The information from the table can also be shown as:

11

B

5

WHAT IT MEANS The Atomic Number: 11

B

= number of protons

5

= number of electrons (as an atom has the same of each) The Mass Number:

= number of protons + neutrons - why are electrons not included in the mass no? They have no mass! So for Boron… What about Phosphorus? Protons = 5

Protons =

Electrons = 5

Electrons = 15

Neutrons = 5.811

Neutrons = 16

15

Learning Check Select the correct symbol for each: A. Calcium 1) C 2) Ca 3) CA B. Sulfur 1) S

2) Sl

3) Su

C. Iron 1) Ir

2) FE

3) Fe

Learning Check Select the correct name for each: A. N 1)neon 2)nitrogen 3)nickel B. P 1)potassium 2)phlogiston 3)phosphorus C. Ag 1) silver

2)agean

3)gold

States of Matter • Matter can exist in 3 states – SOLID – LIQUID – GAS

• The states can change depending on whether we add or remove energy (heat) • Walk on custard

ELECTRON ARRANGEMENT Electrons are very fast moving. They are arranged in shells around the nucleus using the rule 2,8,8,2. The first shell fits up to… 2 e The second fits up to…

8e

The third fits up to… 8 e So the electron shell arrangement for

12Mg

would be…

2, 8, 2 Interactive periodic table

GROUPS The columns in the periodic table are called groups. Groups of elements share similar reactivity. This is because they have the same number of valence electrons. As you go down a group the reactivity increases. Group 1 are the alkali metals properties:

good conductors solid at room temperatures can be cut with a knife low densities and melting points

Group 17 are the Halogens

Periods • The rows in the periodic table are called periods. • Atom’s size decreases from left to right in a given period

Learning Check A. Element in Group XVII, Period 4 1) Br 2) Cl 3) Mn

B. Element in Group II, Period 3 1) beryllium

2) magnesium

3) boron

IONS An ion is an atom that has gained or lost electrons meaning it is negatively or positively charged. Atoms do this to get a full outer (valence) electron shell and so becomes more stable. The atom will get a full outer shell the simplest way it can, e.g. for 12Mg: - Electron arrangement of 2, 8, 2 - it will LOSE 2 electrons (become 2, 8) - Now it has 10 electrons, but still has 12 protons. It has a 2+ charge. The ion is called Mg2+. Superscript is used If an atom loses electrons to for ion charges become stable it will form a positive ion

IONIC COMPOUNDS The ions that have been formed are now attracted to oppositely charged ions. So Mg2+ will be attracted to Cl-. This forms an ionic compound.

Some ionic compounds are soluble others are insoluble. Compounds which are insoluble form solids called precipitates. Lets do an experiment

Difficult Ions Ions

Name

NO3-

Nitrate

CO32-

Carbonate

HCO3-

Bicarbonate or hydrogen carbonate

OH-

Hydroxide

SO42-

Sulfate

S2-

Sulfide

NH4+

Ammonium

PO43-

Phosphate

Difficult Ions Ions

Name

NO3-

Nitrate

CO32-

Carbonate

HCO3-

Bicarbonate or hydrogen carbonate

OH-

Hydroxide

SO42-

Sulfate

S2-

Sulfide

NH4+

Ammonium

PO43-

Phosphate

IONIC FORMULAE So Mg2+ will be attracted to Cl-. Because Mg is 2+ and Cl is only 1-, Mg will attract 2 Cl’s. The subscript shows that they are 2 Cl’s for each Mg. If the starting ions were Cu2+ and S2-, the 2 ions have the same charge. So each Cu will only attract 1 S. The compound formed will be MgCl2.

The compound formed will be CuS.

There is never any charges on the final product they balance out

Conductivity Conductivity is the movement of charged particles. In electricity the particle that moves is usually an electron. What is the charge on an electron? When ionic compounds are dissolved in water they break apart again so the charged particle is the ion. What are the charged particles involved when NaCl is dissolved in water? Will NaCl(s) conduct electricity? What about if it is dissolved NaCl(aq)? Does water conduct electricity?

Solubility • If a solid compound dissolves in a solvent we say it is soluble. • Not all solids will dissolve in water but some may dissolve in another type of liquid. • Water is the universal solvent.

Polymers • Some compounds may form long chains of repeating units (monomers), these form polymers. • Longer chains get tangled more and this affects their properties. • Kevlar and nylon are examples of polymers.

Physical Properties The characteristics of a substance that can be observed without changing the substance.  Colour  Size  Shape  Density  Freezing and Boiling Points  Odour

Metals and Nonmetals Metals  Located to the left of the periodic table  Shiny, ductile  Good conductors of heat and electricity Non-metals  Located to the right of the periodic table  Dull and brittle  Poor conductors, good insulators

Rates of Reaction • Factors increasing the rate of reaction –Surface area –Concentration –Temperature –Catalyst/Enzyme –Pressure

Metal reactions • Metal + Acid → Metal salt + Hydrogen • Mg + HCl → MgCl2 + H2

• Design an experiment to compare how the rate of a reaction changes with increasing concentration of acid. • You can change the concentration of acid by diluting it with water. • When I have seen your method and results table you can perform and write up the experiment.

Metal reactions • Metals corrode in the presence of water and oxygen. • Only Iron rusts! • Metal + Oxygen → Metal oxide • Al + O2 → Al2O3

• Why is Al used for window frames? • Metal + Water → Metal hydroxide + Hydrogen • Al + H2O → Al(OH)3 + H2

H.M.S. Sheffield

Protecting metals • Paint • Oil • Sacrificial (galvanising) • Zn on Fe

• Alloys