ATOMIC DETECTIVE
What are the three subatomic particles found in an atom?
Protons, electrons and neutrons
What is the difference between an element and a compound?
An element contains only one type of atom.
A compound contains two or more different elements chemically bonded together.
An element has the electronic configuration 2,8,2.
Which period is it in?
Answer:
Period 3
What is meant by the term solubility?
The maximum mass of solute that dissolves in 100 g of solvent at a specified temperature.
What happens to the particles when a solid is heated?
They gain energy and vibrate/move more.
Which has the largest mass?
A. Electron
B. Proton
C. Neutron
Answer: C — neutron
Classify each as an element, compound or mixture:
A.Oxygen
B. Water
C. Air
D. Copper
A. Oxygen → Element
B. Water → Compound
C. Air → Mixture
D. Copper → Element
Why do elements in the same group have similar chemical properties?
Answer:
They have the same number of electrons in their outer shell.
What is a saturated solution?
Answer:
A solution containing the maximum amount of dissolved solute at a particular temperature.
In which state can particles move past one another but remain relatively close together?
Liquid
An atom has 17 protons and 18 electrons. Is it neutral? Explain.
No. It has one more electron than proton, so it has an overall 1− charge.
a) Why can a solid not easily be compressed?
b) Why can a gas be compressed easily?
Its particles are already very close together, with very little space between them.
Gas particles are far apart, with large spaces between them.
Electronic configuration
P- 2,8,1
Q- 2,8,7
R- 2,8,8
a) State the group of P.
b) State the group of Q.
c) Which element is most likely to be chemically unreactive?
d) Explain why P and Q are likely to form a compound.
a) One
b) seven
c) R
d)P can lose one electron while Q can gain one electron, allowing both to achieve a stable full outer shell.
Solubility is measured in what units?
g per 100 g of solvent
A student places equal volumes of water into two beakers.
An equal amount of coloured solution is added to each beaker. The water is not stirred.
a) In which beaker will diffusion occur faster?
b) Explain your answer using the particle model.
c) Describe what happens to the concentration of the coloured particles as diffusion continues.
a) Beaker B, at 60°C.
b) At the higher temperature, the particles have more kinetic energy and move faster. Therefore, the coloured particles spread through the water more quickly.
c) The coloured particles move from regions of higher concentration to lower concentration until they become more evenly distributed.
An unknown element X has a mass number of 35 and contains 18 electrons.
a) Is X an atom or an ion?
b) Calculate the number of protons.
c) Calculate the number of neutrons.
d) State the electronic configuration of the neutral atom of element X.
e) State the group and period of X.
Since it has 18 electrons but the element has 17 protons, it has gained one electron.
a) It is an ion.
b) Protons = 17
c)
35−17=1835-17=\boxed{18}
Neutrons = 18
d) Neutral atom:
2,8,7
e)
Group = 7
Period = 3
An unknown element X has a mass number of 35 and contains 18 electrons.
a) Is X an atom or an ion?
b) Calculate the number of protons.
c) Calculate the number of neutrons.
Since it has 18 electrons but the element has 17 protons, it has gained one electron.
a) It is an ion.
b) Protons = 17
c)
35−17=18
A substance has a solubility of 80 g per 100 g water at 50°C.
How much can dissolve in 25 g of water?
20g
Compare the particles in a solid and a gas in terms of arrangement, movement and energy.
An atom has electronic configuration 2,8,7.
Identify:
Why?
It has seven electrons in its outer shell and will gain one electron to achieve a full outer shell.
A student has a mixture of sand, salt and water. Describe how they could obtain the salt.
An unknown element has:
Give:
At 80°C, the solubility of a salt is 120 g per 100 g of water.
A student dissolves 120 g of the salt in 100 g of water at 80°C and then cools the solution to 20°C.
At 20°C, the solubility is 30 g per 100 g water.
How much salt crystallises out?
At 80°C:
120 g dissolved
At 20°C:
Only 30 g remains dissolved.
Therefore:
120−30=90g120-30=\boxed{90g}
90 g crystallises out.
student says, "When a solid melts, the particles become bigger." Explain why this is incorrect.
The particles themselves do not become bigger. They gain energy, move more freely and change from a fixed arrangement to a less ordered arrangement.