The periodic table Flashcards
How did Mendeleev arrange elements in the periodic table?
- First in order of increasing atomic weight
- Then he switched the order of some elements so that they fitted the pattern of others in the same group
- Left gaps for elements that hadn’t been discovered
What happens to metals when they react?
They lose electrons to form a full outer shell (positive ions)
Group 1 - Alkali metals:
- 1 electron in outer shell
- React vigorously with water to create an alkaline solution and hydrogen
- React with oxygen to create an oxide
- React with chloride to form a white precipitate
- The reactivity of the elements increases as you go down the group
Group 7 - Halogens:
- 7 electrons in outer shell
- Non-metals
- Every element forms a molecule of two atoms joined by a covalent bond
- Melting and boiling points increase as you go down the group
- Reactivity decreases as you go down the group
- The molecules get bigger down the group
- A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt
Who was Dmitri Mendeleev?
He developed the first modern periodic table
What qualities do elements in the same group share?
The same amount of electrons in their outer shell, giving them similar chemical properties
When do atoms become ions?
- When they lose or gain electrons
- The positive charges from the protons and the negative charges from the electrons no longer cancel so the atom is now charged
Why does the reactivity of Group 1 increase as you go down the group?
- As you move down the group, the radius of the atom increases, meaning there is a greater distance between the positive nucleus and the negative outer electron - so it is less attracted
- Shielding decreases attraction between nucleus and outer electron. This makes the outer electron easier to lose. Shielding increases as you go down the group because they have more shells.
Properties of metals:
- Very strong, as the ions are held together by metallic bonds
- Malleable
Properties of non-metals:
- Brittle
- Poor conductors of heat and electricity
- Gain electrons in chemical reactions
How does Group 7 react with non-metals and metals?
- React with non-metals to form covalent compounds
- React with metals to form an ionic compound
What state are the Group 7 elements in at room temperature?
Fluorine + Chlorine = gases
Bromine = liquid
Iodine = solid.
What is shielding?
Where inner electrons repel outer electrons, reducing the attraction between the nucleus and the outer shell
Group 0 - The Noble Gases:
- Unreactive as they have a full outer shell meaning they are stable
- All gases as their boiling points are lower than room temperature
- Boiling point increases as you move down the group
- Reactivity increases down the group
