CHAP 3 ATOMIC STRUCTURE

Question 1

state relative charge & approx. relative masses of a proton, a neutron and an electron

Answer 1

proton - 1(relative mass) , +1 (charge)
neutron- 1(relative mass) , 0 (charge)
electron- 1/1840 (relative mass) , -1 (charge)

Question 2

describe the structure of an atom as consisting of protons and neutrons (nucleons) in the nucleus and electrons arranged in shells ( energy level )

Answer 2

1) Proton and neutrons are found in the nucleus of an atom-> collectively known as nucleons
2) Electrons are found outside of the nucleus -> arranged in shells also referred to as energy levels ( surrounding the nucleus )

Question 3

define the term ISOTOPES

Answer 3

atoms of the same element that have different number of neutrons -> share same chemical properties and may differ in physical properties

Question 4

define PROTON number

Answer 4

known as atomic number, gives the number of protons and electrons of an atom.
* number of ELECTRONS = number of PROTONS in an atom

Question 5

define NUCLEON number

Answer 5

known as mass number-> gives the total number of protons & neutrons in the nucleus of an atom.

Question 6

interpret 12
C
6

OR 35 Cl -
17

Answer 6

bottom number/ 6 -> proton number
no. on top/ 12 -> nucleon number
C- atomic symbol of the element
electron no. = 12-6=6
- ( the charge of the ion )

Question 7

describe the differences between elements, compounds and mixtures
+ how compounds can be separated

Answer 7

ELEMENT- pure substance that cannot be broken down into simpler substances by chemical or physical methods ( example: magnesium MG2 , oxygen O2 )

COMPOUNDS- pure substance containing two or more elements that are chemically combined in a fixed ratio-> elements chemically bonded to form either covalent compound or ionic compound
* can be separated by:
1) exposing compounds to strong heat ( thermal decomposition )
2) passing an electric current through the compound ( electrolysis )

MIXTURES- pure substance containing two or more elements that are mixed together in variable ratios
* can be separated by
1) filtration
2) chromatography
3) distillation

Question 8

describe the general properties of metal

Answer 8

1) usually have high densities, melting points and boiling points ( except group 1 ALKALI metals )
2) good conductors of heat and electricity, often shiny, ductile & malleable

Question 9

describe ALLOY and the different types of alloys

Answer 9

a mixture of metal and one or more other elements ( may be metal or non metal )
1) mild steel - iron & carbon -> car bodies , steel rod -> strong & malleable
2) stainless steel - iron, carbon, nickel, chromium -> utensils/ surgical instruments -> non corrosive & Rust resistant
3) brass- copper& zinc -> coins, decorative ornaments-> non corrosive & attractive appearance

Question 10

describe why PURE METALS are soft

Answer 10

due to the regular arrangement of the atoms in the metal lattice-> arranged in neat layers which slide past one another easily when force is applied

Question 11

describe why ALLOYS are stronger

Answer 11

due to the regular arrangement being disrupted by the atoms of different sizes, prevents the layers of atoms from sliding easily making alloys harder than pure metals