chemical patterns

Question 1

whats the equation for the reaction between sodium and chlorine?

Answer 1

sodium + chlorine —> sodium chloride

2Na + Cl2 —> 2NaCl

Question 2

how does sodium react with chloride?

Answer 2

vigorously, to give a yellow flame

Question 3

whats the equation for the reaction of group 1 elements with water?

Answer 3

metal + water —> metal hydroxide + hydrogen

Question 4

what are group 1 metals?

Answer 4

flammable, hydroxides harmful and corrosive

should be kept away from water and naked flames

Question 5

when working with halogens, what should you do?

Answer 5

• safety glasses
• avoid working near naked flames
• watch teacher demonstrations carefuly
• make sure room is well ventilated

Question 6

what are common safety precautions for handling hazardous substances?

Answer 6

• safety screens
• wearing gloves
• eye protection
• washing hands after handling chemicals
• working in fume cupboard

Question 7

what is a group?

Answer 7

vertical column of elements that have similar properties

Question 8

what do group 1 elements include?

Answer 8

• lithium
• potassium
• sodium

Question 9

what is the relationship between the group # and # of electrons?

Answer 9

group # corresponds to # of electrons in outer shell of atom

group 1 elements have 1 electron in outer shell
group 7 elements have 7 electrons in outer shell

Question 10

what is a period?

Answer 10

horizontal row of elements

Question 11

what are examples of elements in the same period?

Answer 11

• lithium
• neon
• carbon

Question 12

what are the steps to write a balanced equation?

Answer 12

1) write word equation
2) substitute formulae for names of elements/compounds involved
3) balance equation by adding # in front of reactants/products
4) write balanced symbol equation

Question 13

what is the name of group 1?

Answer 13

alkali metals

Question 14

what happens if you go further an element down the group?

Answer 14

• higher reactivity
• lower melting and boiling points
• higher density

Question 15

what is the trend in group 1 metals?

Answer 15

have 1 electron in outer shell

more reactive down group

Question 16

what should you do when working with group 1 metals?

Answer 16

• use small amounts of metals
• safety glasses
• watch teacher demonstrations carefully
• ensure metals stored under oil
• avoid working near naked flames

Question 17

what do alkalis react to form?

Answer 17

compounds

Question 18

what do alkali metals look like?

Answer 18

shiny when freshly cut, but tarnish in moist air, go dull and become covered in metal oxide

Question 19

how do alkali metals react with chlorine?

Answer 19

vigorously to form white crystalline salts

Question 20

whats the general equation where M refers to the alkali metal?

Answer 20

2M + Cl2 —> 2MCl

eg

lithium + chlorine —> lithium chloride
2Li + Cl2 —> 2LiCl

Question 21

what do alkali metals react with water to form?

Answer 21

metal hydroxide and hydrogen gas, mh dissolves in water to form alkaline solution:
2M + 2H20 —> 2MOH + H20

eg:
potassium + water —> potassium hydroxide + hydrogen
2K + 2H20 —> 2KOH + H2

Question 22

what are examples of reactivity of alkali metals increasing further down a group?

Answer 22

• lithium, reacts quickly, water
• sodium, reacts vigorously, water + melts
• potassium, reacts vigorously, water that sparks produce

Question 23

what is the names of group 7?

Answer 23

halogens

Question 24

what can you use halogens for?

Answer 24

• bleach dyes

- kill bacteria in water

Question 25

at room temp and pressure, what happens?

Answer 25

``` chlorine = green gas bromine = brown liquid iodine = dark purple solid ```

Question 26

what do all halogens consist of?

Answer 26

diatomic molecules | only exist in pairs of atoms

Question 27

halogens react with alkali metals to produce water? | give an example

Answer 27

halides lithium + chloride ---> lithium chloride 2Li + Cl2 ---> 2LCl

Question 28

what is the trend in group 7?

Answer 28

7 electrons in outer shell less reactive going down group

Question 29

what should you do when working with halogens?

Answer 29

- safety glasses - work in fume cupboard - use small amounts of dilute conc - room = ventilated

Question 30

what are ions?

Answer 30

atoms that've gained/lost electrons as # of protons + electrons not equal, ions have overall charge

Question 31

what is ionic bonding?

Answer 31

occurs between metal + non metal

Question 32

electrons transfer from 1 atom to another to form electrically charged ions how?

Answer 32

- atoms that lose electrons become positively charged ions | - atoms that gain electrons become negatively charged ions

Question 33

compounds of group 1 and 7 elements are what?

Answer 33

ionic compounds (salts). - IC form crystals bc irons arranged into regular lattice

Question 34

what happens to ionic crystals when they melt/dissolve in water?

Answer 34

they conduct electricity --> bc charged ions are free to move around

Question 35

what is inside an atom?

Answer 35

has nucleus made up of protons and neutrons surrounded by electrons in shells

Question 36

what do all protons and atoms have?

Answer 36

atom: - same # of protons as electrons so atom is neutral - atoms of same element have same # of protons proton: - same mass as neutron, mass of an electron is negligible

Question 37

what does the electron configuration of an atom show?

Answer 37

how electrons are arranged in shells around the nucleus

Question 38

what is spectroscopy?

Answer 38

when elements are heated, they emit distinctive coloured flames light emitted produced line spectrum each element, own spectrum study of spectra used to analyse unknown substances + discover new elements eg helium ---> first seen in light from sun

Question 39

what are the colours of elements when heated?

Answer 39

sodium - yellow potassium - lilac lithium - red

Question 40

how do you write a balanced equation?

Answer 40

follow these steps... 1) write word equation 2) substitute formulae 3) balance by adding # 4) write balanced equation

Question 41

how do halogens react with other elements?

Answer 41

form compounds reaction with alkali metals highly exothermic forming ionic compounds eg: lithium + bromine ---> lithium bromide 2Li + Br2 ---> 2LiBr

Question 42

what is the displacement reactions of halogens?

Answer 42

reactive halogen displace less reactive halogen from an aqueous solution of its salt meaning chlorine will displace both bromine and iodine, while bromine will displace iodine eg: potassium iodide + chlorine ---> potassium chloride + iodine 2Kl + Cl2 ---> 2KCl + l2

Question 43

what are the properties of compounds of halogens with alkali metals?

Answer 43

compounds of alkali metals and halogens conduct electricity when molten or dissolved in water made up of ions

Question 44

what are ionic compounds?

Answer 44

electrically neutral substances that have positive and negative charge

Question 45

what is the history of the periodic table?

Answer 45

Dobereiner said some elements with similar properties formed groups of 3 - triads eg lithium, sodium and potassium Newlands said when elements were arranged in order of increasing atomic weight, some repeating patterns in properties could be seen - law of octaves Mendeleevs table allowed similar elements to be grouped together and show repeating patterns - left gaps in table for non discoveries

Question 46

what is the table of atom particle?

Answer 46

atom particle relative mass relative charge p 1 +1 n 1 0 e nearly 0 -1

Question 47

what are elements?

Answer 47

made of only 1 kind of atom, all atoms of an elements have same number of protons diff elements have diff proton numbers and arranged in a order of increasing proton number in the pt giving repeating patterns in properties of elements

Question 48

what happens when lithium, potassium and sodium react with cold water?

Answer 48

- float due to low density | - produce bubbles of hydrogen gas