EOY
暂无描述。系统推荐的高质量记忆内容，适合每天坚持背诵学习。
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Advantages of nanoparticles in suncream?
better coverage more protection from the sun’s UV rays
Disadvantages of nanoparticles in suncream?
may cause potential cell damage to the body could have harmful effects on the environment
Order of sizes
dm, cm , mm , um (micrometre), nm
Pure substance
a single element or single compound
What is the test for chlorine gas?
a damp litmus paper turns white
oxides of nitrogen cause
acid rain
particulate matter causes
global dimming
what is the relative mass of an electron?
very small
what is the relative mass of a proton and neutron?
1
Why are instrumental methods used to measure gas?
accurate
Compounds formed from only non-metals consist of particles called?
molecules
Compounds formed when non-metals react with metals consist of particles called?
ions
The relative formula mass of a substance, in grams, is one … of the substance
mole
Why did Mendeleev leave gaps?
for undiscovered elements
State two similarities between hydrogen and atoms in group 1?
they have 1 electron in their outer shell forms ions with a 1+ charge
Describe how knowledge of the numbers of protons and electrons in atoms allow chemists to place elements in their correct order and correct group.
number of electrons = number of protons chemical properties depend on the outer electrons number of shells gives the period
There are no transition elements between the Group 2 element magnesium and the Group 3 element aluminium. Give a reason why, in terms of electronic structure.
2nd shell can only have a maximum of 8 electrons
Suggest what predictions Mendeleev was able to make about these undiscovered elements.
predicted their properties predicted that they were metals
Why is lithium less reactive than potassium, in terms of electronic structure?
outer shells are closer to the nucleus stronger force of attraction between the outermost electron and the nucleus, less easily lost in reaction
State why transition metal oxides are added to pottery glazes
For colour
State two properties which coinage metals should have
hard - so they don’t get scratched unreactive - so they don’t corrode
Explain 2 differences in the reactions of potassium and lithium with water
potassium produces a lilac flame melts and forms a ball
Give 3 properties of why alkali metals should be grouped together
they form ions with 1+ charge they are very reactive they react with water to form alkaline solutions
How did Mendeleev improve John Newland’s periodic table and why?
he left gaps for undiscovered elements so that the elements would fit into their proper groups