Periodic Table Flashcards
Across the Periodic Table, the elements gradually…
Across the periodic table means from left to right
From left to right,
- increasing proton, atomic and mass no.
- change from metallic properties to non-metallic properties
What does the group number tells you about the electrons?
Group no. tells the no. of valence electron
For example, Group 2 elements have 2 valence electrons
This thus also tells us the charge of the ion, Group 2 elements have 2 valence electron, need to lose 2 electrons and therefore have a charge of 2+
What does the period number tells you about the electrons?
Period no. tells the number of electron shells in an element
For example, Period 2 elements have 2 electron shells, Lithium is from period 2, there it has 2 electron shells, Lithium 2,1
How are the elements in a periodic table arranged?
In increasing atomic number
atomic no. is proton no.
Why are alkali metals so reactive?
All atoms want to obtain a full valence electron shell to be stable.
As Group 1 metals only have 1 valence electron,
It is easier to lose that 1 electron to obtain a full valence shell, forming a positive ion.
Physical properties of Group I metals
Physical properties of Group 1 metals:
- Soft and can be cut easily with a knife
- Low density
- Low m.p & b.p
Opposite of what you usually expect of a metal- hard, heavy, high melting point.
As we go down the Group I elements,
group 1:
- melting and boiling point decreases
- reactivity increases
What is the name of Group I metals?
Alkali metals
Group I metals react with water to form …?
Group I metals react with water to form alkali (metal hydroxide) and hydrogen gas
General formula:
2X + H20 2XOH + H2
X is a group I metal
How to test for the gas when Group 1 metals react with water?
When group 1 metals react with water, you’ll get hydrogen gas
to test for hydrogen gas, insert a lighted splint into a test tube and it would extinguish with a ‘pop’ sound
Describe the observation when Lithium reacts with water
Lithium reacts quickly with water and floats on water surface
Describe the observation when Sodium reacts with water
Sodium reacts violently with water and darts around the water surface (might be explosive)
Describe the observation when Potassium reacts with water
Potassium reacts explosively with water and darts around the water surface
Explain why does the reactivity increases when it goes down Group 1
As you go down the group,
the elements have more electron shells
this means that the valence electron shell is further away from the nucleus.
This weakens the attractive force between the nucleus and the valence electron shell
and thus making it easier to lose the valence electrons to form ions
What is the name of Group 7 elements?
Halogens
State the colour and state at rtp of Group 7 elements
Fluorine, Chlorine, Bromine, Iodine
Fluorine: Pale yellow Gas Chlorine: Greenish-yellow Gas Bromine: Reddish-brown Liquid Iodine: Purplish-Black Solid However, at Aq state-brown, at gas state-purple
As we go down group 7…
- m.p and b.p increases
- reactivity decreases
- the colour gets darker
Why does the reactivity decrease when it goes down group 7?
As it goes down the group, there are more electron shells and the valence electron gets further away from the nucleus, thus the attractive force gets weaker and weaker which makes it harder to gain an electron.
Group 7 is the most reactive non-metals while Group 1 is the most reactive metals. Is this true?
Yes, because group 7 just need to gain one electron while group 1 only needs to lose one electron.
What type of molecules do Group 7 elements form?
State some examples.
Group 7 forms diatomic molecules
F2, Cl2, Br2, I2. At2
Group 7 react with metals to form an ionic bond. What is the name of the ion?
Group 7 elements gain one electron having a charge of 1-, becoming a halide.
Halides: Fluoride F-, Chloride Cl-, Bromide Br-, Iodide I-
What’s a displacement reaction?
-note: there’s no need to memorise this definition, it’s just for understanding!
displacement reaction is where a more reactive halogen replaces a less reactive halogen.
Chlorine is added to potassium bromide.
State the equation, observation and explanation.
Equation: Cl2 + 2KBr > 2KCl + Br2 (all aq)
Observation: colourless solution turns brown
Explaination: As chlorine is more reactive than bromine, chlorine displaces bromine from the bromide solution.
Bromine is added to potassium bromide.
State the equation, observation and explanation.
Observation: No visible change
Explanation: Both halogens have the same reactivity, bromine cannot displace the bromide solution.
