Atomic Structure and Bonding

How was early periodic table arranged?

• Arranged by physical and chemical properties

• Arranged by atomic weight

Why is the table called a “periodic” table?

• The table is called a periodic table because similar properties occur at regular intervals

How were elements placed incorrectly in early tables?

• Order of atomic weight rather than mass

• Not all elements were present as some we undisocvered

• Didnt take into account chemical properties

How did Mendeleev present his periodic table?

• Order elements by increasing atomic weight

• Arranged elements that had similar properties in rows (periods) and columns (groups)

• He left gap and predicted properties for undiscovered elements

Why was mendelev theory validated?

• Newly discovered elements fitted with Mendelev predictions

• Isotopes had different masses but same properties so he was correct group them with other elments with the same properties

How are elements arranged in modern periodic table?

• Increasing atomic number

• Patterns of chemical and physical properties (periods/groups)

Groups

• Elements in same group have similar properties

• As they have the same no of electrons in their outershell

Period

Tells use how many shell each atom has

How did Mendeleev know of undiscovered elements?

• If placed consecutively some elements would be placed into groups which had diff chemical properties than other elements

• This mean they were in the wrong group

What happens as elements go down in the group?

• As elements go down in the group

• Number of electron shells increase

• Which means it decreases in reactivity down group 7

• Increases in reactivity down group 1

Metals

• Positive Ions when they react

• Found further down periodic table and to the left hand side

• Elements in the centre of periodic table are known as transition metals

• Majority of elements are metals

Non Metals

• Negative Ions when they react (or covalent bonded)

• Right hand side of staircase non metals

Physical Properties of Metals

• Strong (hard to break)

• Malleable (bent or hammered into shape)

• Ductile (can be shaped into wires)

• Good conductors of electricity and heat

• High Melting and Boiling Points

• Dense

• Shiny

Physical Properties of Non Metals

• Brittle (snap easily)

• Dull (not shiny)

• Lower mp and bp

• Poor conductors of electricity

• Lower density

3 Properties of Transitional Metals

• they make good catalysts (iron catalyst in haber process)

• ions are often coloured so they can form colourful compounds

• can have more than one ion (Cu 2+ and Cu +) ions

Properties of Group 1 Metals

• Soft

• Low density

• Very Reactive

• Weak

• Relatively low melting points (compared to other metals)

Group 1 Metals

• Alkali Metals

• Silvery solids that have to be stored carefully with oil etc..

• Characteristic properties as:

• All have one electron in outer shell which makes them very reactive and means they react in similar ways

• eg. low density

Reactivity + Why in Group 1

• As you go down the group increases distance (atomic radius) and shielding increase

• Meaning there is a weaker electrostatic attraction between outermost (valence) electron and the nucleus

• Means that the amount of energy required to lose the outer most electron decreases which makes it easier for reaction to occur