Jan 9 Flashcards

Question

Element

Answer 1

Element is a pure substances which cannot be broken down into anything simpler by chemical methods.

Answer 2

Compound is a pure substance that contains two or more different kinds of element that is chemically bonded. Its formation is a chemical change in which new substances are formed. It can be separated into its constituent by chemical methods.

Answer 3

Mixture is a substance that contains two or more different kinds of substances that are not chemically bonded. Its formation is a physical change in which no new substances are formed. It can be separated into its constituents by physical methods.

Answer 4

Isotopes are different atoms of the same element that have the same number of protons but a different number of neutrons

Answer 5

Relative abundance is the distribution of isotopes in nature of an element.

Answer 6

Relative isotopic mass of a particular isotope of an element is the mass of an atom of the isotope relative to the 1/12 of the mass of a carbon-12 atom.

Answer 7

Relative atomic mass of an element is the average isotopic mass of all the natural isotopes on the 12C=12.00 scale.

Answer 8

1. Atomic size increases from left to right as the attraction between electron and the nucleus increases 2. Group I to III mp and bp increases as metallic bond strength increases with increasing number of outermost electrons Group IV mp and bp is maximum as its element has giant covalent structure Group V to VII mp and bp is low as they have weak van Der Waals' forces exist between molecules Group 0 mp and bp are low because they are all monatomic molecules, weak van Der Waals' forces exist between molecules 3. ability to attract electrons increases across the period as the number of protons increases across the period which causes increased attraction between incoming electron and nucleus.

Answer 9

1. Atomic size increases down the group as the number of occupied electron cells increases down the group 2. Group I to II mp and bp decreases down the group as atomic size increases down the group, attraction between cations and delocalised electrons in the metal decreases which leads to weaker metallic bond. Group VII to 0 increases down the group as molecular size increases down the group, leads to increasing length of van Der Waals' forces. 3. Ability to attract electrons decreases down the group as the number of occupied electron shells increases down the group which there is a weaker attraction between the incoming electrons and the nucleus.

Answer 10

alkali metals reactivity increases down the group soft and can be cut by a knife shiny when freshly cut but tarnish easily low density low mp and bp react with oxygen to form metal oxide react with water to form metal hydroxide (Li fizzes steadily on water surface, Na melts to form a silvery ball and fizzes quickly on water surface, K melts to form silvery ball and fizzes furiously on water surface, hydrogen gas catches fire and produce a lilac flame react with chlorine to form metal salts

Answer 11

alkaline earth metals reactivity increases down the group (less reactive than alkali metals as they need to lose more electrons than alkali metals) soft but harder + denser than alkali metals shiny when freshly cut and tarnish easily high mp or bp reacts with oxygen to form metal oxide when heated in air reacts with dilute hydrochloric acid to form metal chloride and hydrogen gas (metal dissolves and gas bubbles are evolved) reacts with chlorine to form metal salts some reacts with water to form metal hydroxide + hydrogen (Mg reacts very slowly with water, Ca reacts readily and gives steady stream of gas bubbles)

Answer 12

halogens reactivity decreases down the group mp and bp increases down the group F is pale yellow gas Cl is greenish yellow gas Br is reddish brown liquid (vaporise easily to give orange vapour) I is black solid (sublimes easily to form purple vapour) At is black solid poor conductors of electricity colours are darker down the group less volatile down the group reacts with hydrogen to give hydrogen halides

Answer 13

noble gases stable because it fulfils octet rule / duplet rule reactivity decreases down the group colourless low mp and bp very low density poor conductors of heat and electricity reacts with fluorine under special condition (Kr, Xe)

Answer 14

advertising signs as it produces a distinctive red-orange light when electricity is passed through it

Answer 15

added to the space above wine in wine barrels to stop oxygen in air to react with wine as argon is denser than air fill tungsten light bulbs because it does not react with the hot tungsten filament

Answer 16

Monatomic ion is an atom that loses or gains one or more electrons

Answer 17

Polyatomic ions are ions that are formed from a group of atoms

Answer 18

Conductors are substances which conduct electricity but are not chemically changed during electrical conduction

Answer 19

Electrolytes are substances which conduct electricity in molten state or aqueous solution but not in solid state and are decomposed during conduction.

Answer 20

Non-conductors are substances which do not conduct electricity in solid, molten state or aqueous solution

Answer 21

Ionic bond is the strong electrostatic forces of attraction between oppositely charged ions. An ionic bond is formed when electrons are transferred from one atom to another. When metal reacts with non-metal to combine to form an ionic compound. Electrons are transferred from atoms of the metal to the atoms of the non-metals.

Answer 22

ammonium chloride ammonium sulphate

Answer 23

Metallic bond is the strong electrostatic force of attraction between the positive metal ions and the "sea" of delocalised electrons.

Answer 24

Covalent bond is the strong electrostatic force of attraction between positively charged nuclei of two bonded atoms and the negatively charged shared electrons. Covalent bond forms when two atoms share a pair of electrons.

Answer 25

Hydrogen Oxygen Chlorine Nitrogen

Answer 26

Lone pair of electrons is a pair of electrons in the outermost shell of one of the atoms in a molecule which is not involved in the bonding.

Answer 27

Dative covalent bond is a type of covalent bond in which lone pair of electrons come from the same atom.

Answer 28

1. usually in crystalline form 2. high mp and bp as ions are held by strong ionic bonds 3. solid compounds do not conduct electricity because the ions are not mobile 4. molten state or aqueous solution compounds conduct electricity because ions are mobile 5. hard because ions are held together closely by strong ionic bonds 6. brittle because ions are attracted by strong ionic bonds. when a force is applied, ions of the same charge may come together and cause repulsion. solid breaks apart 7. high density because ions are held by strong ionic bond 8. soluble in water but insoluble in non-aqueous solvents

Answer 29

Attractive force between its particles and solvent particles are strong enough to overcome attractive forces between particles in pure substances. particles in substance must separate from each other and surrounded by solvent particles.

Answer 30

Allotropes are two or more forms of the same element in which the atoms or molecules are arranged in different ways.

Answer 31

Diamond, Graphite, Silicon dioxide, Silicon

Answer 32

a carbon atom is tetrahedrally bonded to four other carbon atoms covalent bonds are extended in all directions throughout the structure

Answer 33

layered structure carbon atoms in the same layer are held together by strong covalent bonds weak van Der Waals' forces exist between the layers can conduct electricity in the graphene plane as there is delocalised electrons in the outermost shell can be used as making because as layers of graphite are only attracted by weak van Der Waals' forces so that the layers can slide past each other easily

Answer 34

1. High mp and bp because atoms are held together by strong covalent bonds 2. Do not conduct electricity because there are neither mobile ions or delocalised electrons (except graphite) 3. Very hard because atoms are held together by strong covalent bonds to form a giant network 4. Insoluble in all solvents because atoms are held together by strong covalent bonds

Answer 35

1. low mp and bp because molecules are attracted by weak van Der Waals' forces only 2. larger molecular size has higher melting and boiling point because the strength of van Der Waals' forces increases as the molecular size increases. 3. Do not conduct electricity in both solid and molten 4. Usually soft because molecules are attracted by weak van Der Waals' forces 5. Usually soluble in non-aqueous solvent and slightly soluble or insoluble in water

Answer 36

1. strength of metallic bond increases from left to right as number of outermost electrons increases. 2. strength of metallic bond decreases as the atomic size increase down the group, attraction between protons in the nucleus and delocalised electrons decreases down the group

Answer 37

metal sulphide is heated strongly in the presence of excess air

Answer 38

carbonate ores is heated strongly in the absence or limited supply of air

Answer 39

Hematite, coke, limestone is added through the top of blast furnace Hot air is blasted near the bottom of furnace Coke burns in air to form carbon dioxide More coke is added (carbon dioxide + carbon --> carbon monoxide) Carbon monoxide acts as reducing agent and reduces haematite Molten iron contains impurities trickling downwards in the blast furnace. Impurities are removed using limestone. Calcium carbonate decomposes under higher temperature (calcium carbonate --> calcium oxide + carbon dioxide) Calcium oxide reacts with impurities to form calcium silicate (from silicon dioxide). Calcium silicate forms a slag which runs down the furnace and floats on top of molten iron. Waste gases (nitrogen and oxide of carbon) escape from top of furnace.