gcse Flashcards
(66 cards)
What’s the atomic theory
The idea that everything is made up from tiny little particles that can’t be broken down any further
And that they’re separated from each other by empty space
Originally proposed by a guy from ancient Greek called Democritus (500B.C)
What’s the difference between covalent and ionic bonding and the properties these bonds have
- Covalent = sharing of electrons between non-metal atoms.
- Ionic = the transfer of electrons from a metal atom to a non-metal atom, forming positive and negative ions.
What’s the differences between covalent and ionic bonding’s in terms of the properties these bonds have
Properties of covalent compounds:
* Usually have low melting and boiling points because of weak intermolecular forces.
* Do not conduct electricity because there are no free ions or electrons.
* Can be gases, liquids, or solids at room temperature.
.
Properties of ionic compounds:
* Have high melting and boiling points due to strong electrostatic forces between ions.
* Conduct electricity when molten or dissolved in water because ions are free to move.
Usually solid crystals at room temperature
What is endothermic reaction
- Endothermic reaction: A chemical reaction that absorbs energy from the surroundings, causing the temperature of the surroundings to decrease.
What is exothermic reaction
- Exothermic reaction: A chemical reaction that releases energy to the surroundings, usually in the form of heat, causing the temperature of the surroundings to increase.
What are the trends in the periodic table for group 7
- Reactivity decreases down the group.
- Melting and boiling points increase down the groups
- Colour of elements becomes darker down the group.
Elements change states (gas-liquid-solid)
Why does the reactivity decreases down the group.
7
- Because they gain electron less easily
- Since there is a greater distance between the outer energy level and the nucleus
Greater shielding of outer electron down
What are the trends in the periodic table for group 8/0
- Boiling points increase down the group.
- Intermolecular forces become stronger down the group.
All elements are VERY unreactive due to a full outer shell of electrons.
What are the trends in the periodic table for group 1
- Reactivity increases down the group. (with o2 as well)
- Melting and boiling points decrease down the group.
- Density generally increases down the group.
Outer electron is more easily lost due to weaker attraction from the nucleus.
Why are group 1 metals more reactive down the line
- As we go down group 1 the radius of the atoms increases.
- This means that there is a greater distance between the positive nucleus and the negative outer electron
- And as this increases the outer electron is less attracted to the positive nucleus
Shielding increases down
Dmitri Mendeleev
- Developed the first periodic table
- He started by arranging all the elements in order of increasing atomic weight
- He then switched the order of specific elements so they fitted the patterns of other elements in the same group
- He left gaps for the undiscovered elements (ones he thought were missing)
- When the undiscovered elements became discovered, their properties matched his predictions
- In result people began to believe that his table is correct
Did not add group 0
More reactive metal displaced less reactive ones from salts and oxides
- A more reactive metal will displace a less reactive metal from its salt solution or oxide
- This is because the more reactive metal forms positive ions more easily
Example: Magnesium + copper sulfate → magnesium sulfate + copper
Isotopes definition
Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
Changes of states
The stronger the forces of attraction between the particles the more energy we have to put in to break these forces
And the higher the melting point
Candle wax is a solid with relatively weak force of attraction meaning they are fairly easy to break (melt)
What did Johann Dobereiner notice
That elements with similar chemical properties often occurred in threes called ‘‘triads’’
e.g
- Lithium
- Sodium
- Potassium
(all reacts rapidly with water)
- Chlorine - Bromine - Iodine
(all reactive non-metal)
Elements definition
a substance made of only one type of atom
It cannot be broken down into anything simpler by chemical means
Compound definition
Contains two or more different elements, chemically combined in fixed proportions
if we want to separate a compound we have to use chemical reactions
Mixture definition
In a mixture, we have different elements or compounds but they are not chemically combined
If we want to separate a mixture we use a physical separation technique
Molecule definition
Has any elements chemically combined, even if they’re the same element
e.g. H2O (both molecule and compound)
What is electrolysis
Using electricity to cause a reaction in a solution or molten ionic compound
numbers of an element in the periodic table
Top - mass number
- (Tells us the total amount of protons + neutrons)
Bottom - the atomic number
(tells us the amount of protons/electron)
Shielding definition
- Shielding is the reduction in the attraction between the nucleus and the outer electrons caused by inner electron shells. ✅
- Inner shells block the attraction of the nucleus, making it easier to lose or harder to gain electrons. ✅
Covalent bond
a shared pair of electrons between two non-metal atoms
Mostly group 7 = (F-F)
Physical states of group 7
- Fluorine = gas
- Chlorine = gas
- Bromine = liquid
- Iodine = solid
