periodic table Flashcards
Thallium (Tl) has proton number 81.Would you expect thallium to be a metal or a non-metal? Give one reason for your answer.
Thallium is a metal. It has three electrons in its valence shell and hence it will lose the 3
valence electrons to form a positive ion to achieve a stable electronic configuration.
what is the trend of oxides across the period
Across the period, the oxides of the elements tend to change from basic to acidic.
what are the Properties of Group I metals
1. how many electrons in the valence shell?
2. how reactive are they?
3. physical characteristics
4. conductor of heat & electricity?
5. density?
6. melting point? (does it increase/decrease down the grp?)
7. reaction with water
8. observation when they react with non metals?
- They have 1 electron in their valence shell. Their atoms react by losing one electron, forming an ion with a charge of 1+.
- They are the most reactive of all the metals. Alkali metals are stored under oil to protect them from oxygen and water vapour in the air
- They are soft and silvery metals.
- They are good conductors of heat and electricity.
- They have generally low densities and can float on water (first 3 Alkali metals). –> increases down the grp
- They have low melting points. –> decreases down grp
- They react violently with water.
- Alkali metals are never found as free elements in nature.
- They tend to react with non-metals forming soluble, white ionic compounds.
reaction of alkali metal with water? (include observations too)
Every Alkali metal reacts with cold water, releasing hydrogen gas and producing a solution of metal hydroxide that is alkaline.
Effervescence is observed as hydrogen gas is produced.
* Darting of the metal piece on the surface of the water.
* Beaker feels warm (heat is produced during the reaction).
* Colourless solution turns pink when phenolphthalein indicator is added to the solution.
what is the trend of reactivity of elements in group 1 down the group?
Reactivity of the elements increases down the group (metallic character increases).
The element shows a more violent reaction with water down the group.
Down the group,
* Number of filled principal quantum shells increases.
* Distance between the nucleus and the valence electron increases.
* Electrostatic forces of attraction between the nucleus and the valence electrons
decreases.
* Thus, less energy is required to remove the valence electron from the atom.
* In conclusion, first ionisation energy of the metals decreases. Thus reactivity of the metals increases.
why does the density of the elements increase down the group.
The densities of Group I Alkali metals are generally lower than other metals. As such, Alkali
metals such as lithium, sodium and potassium tend to float on water.
Properties of Group VII elements
1. electrons in their valence shells?
2. what do they exist as?
3. how do they form into ions?
4. formation of ionic compound?
5. formation of covalent compound?
6. melting point & boiling point?
7. are they conductors of electricity?
Properties of Group VII elements
* They have seven electrons in their valence shells.
* They all exist as diatomic covalently bonded molecules, with the formula X2.
* The atoms react by gaining one electron, forming an ion with a charge of 1−, X−.
* They form ionic compounds with metals e.g. sodium chloride (NaCl) and magnesium fluoride
(MgF2).
* They form covalent compounds with non-metals e.g. hydrogen bromide (HBr), hydrogen
chloride (HCl) and sulfur hexafluoride (SF6).
* They are typical non-metals with low melting and boiling points.
* They are all insulators of electricity.
why does the Melting and boiling point increase down the group as seen in the physical state of the
elements changing from gas → liquid → solid.
Reason: Down the group,
* As the molecular mass of each molecule increases, the strength of the intermolecular
forces of attraction (van der Waals’ forces of attraction) increases.
* More energy is needed to overcome the stronger intermolecular forces of attraction
between the iodine molecules than those between bromine, chlorine and fluorine
molecules.
* (enrichment) A larger electron cloud (larger molecules) translates to stronger intermolecular forces
of attraction due to a higher electron density. (The number of electrons in F2 molecule is
18, Cl2 molecule is 34, in Br2 molecule is 70 and I2 molecule is 106.)
trend of color down the group?
Colour of the element gets darker down the group.
what are halogens?
Halogens are reactive non-metals. They react with most metals to form salts called halides.
Fluoride ions (F−), chloride ions (Cl
−), bromide ions (Br−) and iodide ions (I−) are examples of halide ions.
what do halogens undergo displacement with?
Halogens undergo displacements reactions with halide solutions. A displacement reaction is a
reaction in which one element takes the place of another element in a compound. A more reactive halogen will displace a less reactive halogen from its compound.
what is the reaction between chlorine, Cl2 (aq) (light yellow) and solutions?
1. KCl solution
2. KBr solution
3. KI solution
- No visible reaction.
- Solution turned from colourless to reddish- brown.
Reason: Chlorine displaces bromine from potassium bromide
solution. - Solution turned from
colourless to brown.
Reason:
Chlorine displaces
iodine from potassium
iodide solution.
what is the reaction between bromine, Br2 (aq)
(reddish-brown
or orange) and solutions?
1. KCl solution
2. KBr solution
3. KI solution
- No visible reaction.
- No visible reaction.
- Solution turned from
colourless to brown.
Reason:
Bromine displaces
iodine from potassium
iodide solution.
what is the reaction between iodine, I2 (aq) (brown) and solutions?
1. KCl solution
2. KBr solution
3. KI solution
- No visible reaction.
- No visible reaction.
- No visible reaction
why are the noble gases from group 0 inert gases?
Their inertness or lack of reactivity is due to their stable electronic
configuration. They have complete valence shells. They have little tendency to share electrons
to form a covalent bond or to lose or gain electrons to form an ionic bond. They are electronically
very stable.
