1.6 The Periodic Table Flashcards
Who is the scientist who published his periodic table in 1869 and what did he do for elements that weren’t discovered at that time?
Mendeleev - he left gaps in order that similar elements would fall in the same vertical column.
What is a group and a period?
Group- a vertical columns in the Periodic Table.
Period- a horizontal rows in the Periodic Table.
What are the differences between Mendeleev’s Table and the Modern Periodic Table?
Mendeleev’s Table:
-Elements arranged in order of atomic weight
-No noble gases
-Gaps were left for undiscovered elements
-No block of transition elements
-Actinides and Lanthanides not present
Modern Periodic Table:
-Elements arranged in order of atomic number
-Noble gases added
-No gaps (now know all elements)
-A block of transition elements
-Actinides and Lanthanides present
What is the definition of an element?
An element is a substance that consists of only one kind of atom. Elements cannot be broken down into anything simpler by chemical means.
What are the three physical states of elements?
Solid, liquid or gas
What do these names given to these changes of state mean? : melting, freezing, evaporation, condensation, sublimation and reverse sublimation.
Melting- solid to liquid
Freezing- liquid to solid
Evaporation- liquid to gas
Condensation- gas to liquid
Sublimation- solid to gas
Reverse sublimation- gas to solid
How can you find out the period and group an element is in due to its electronic structure?
Period- the period number is the number of electron shells
Group- the group number is the number of electrons in the outer shell
e.g. Sodium has the electronic figure 2,8,1
-this means sodium is in group 1 and period 3
Describe groups 1,2,7,0 and the transition metals
Group 1- the alkali metals are a group of highly reactive metals.
Group 2- the alkaline earth metals are a group of reactive metals.
Group 7- the halogens are a group of reactive non-metals
Group 0- the noble gases are a group of unreactive non- metals
The transition metals are a block of metals between Group 2 and Group 3
Describe the trends in groups 1,2,7 and 0
Group 1- as we move down group one, the reactivity increases and the melting and boiling points decrease
Group 2- as we move down group two, the reactivity increases and the melting and boiling points decrease (not as reactive as Group 1)
Group 7- as we move down group seven the reactivity decreases and melting and boiling points increase
Group 0- the noble gases elements are unreactive since they have 8 electrons in their outermost shell and so do not need to react to achieve a stable electron structure. As we move down the group the density of the gases increases.
Describe the trends as you move left —> right across period 3
- The number of outer shell electrons increases by 1 each time.
- Each time you start a period; you start a new electron shell.
- Elements go from metals to non-metals. Silicon is in between and is called a semi-metal or metalloid.
- Melting/Boiling Points increase to the middle of the Period then decrease again. They are lowest on the right.
- All elements except argon react with oxygen to form oxides.
- Metal oxides are basic
Non-metal oxides are acidic
Aluminium oxide is both acidic and
basic
It is called an amphoteric oxide.
What are the safety considerations for reacting alkali metals with water?
- Do not handle the metals- use forceps/gloves this prevents the metals reacting with your hands.
- Wear safety glasses- to prevent eye damage for the metals or the products of the reactions.
- Use a safety screen and stand back - prevents metal hitting your skin if it explodes.
- Use small quantities of the metals - reduces explosive risk.
What are the general observations when alkali metals react with water?
Floats; moves on surface; bubbles of gas; metal gets smaller and disappears; heat produced and colourless solution left.
Note: Na and K also melt; only K burns
Why are the alkali metals stored in oil and what happens to the reaction of the alkali metals with water as you descend the group?
-To prevent contact with moisture and oxygen in the air which they would react.
-The alkali metals react more vigorously with water as the group is descended.
Describe the appearance of lithium, sodium and potassium
- Fresh surface is silvery grey with metallic lustre (shiny).
Why does the reactivity of Group 1 metals increase as you move down the group?
-When a Group 1 atom reacts it loses an electron from its outer shell to form a positive ion with a full outer shell.
-Going down the group the atoms get bigger due to there being more shells of electrons. As a result, the outer electron is further away from the positive charge of the nucleus. This means that the outer negative electron is less strongly attracted to the positive nucleus, and so easier to lose. The easier the electron is to lose, the more reactive the alkali metal.
