Organise these statements into chronological order. Then either:
• Create a story board by drawing a picture
above each one to explain what is happening.
• OR if pictures are not your thing, write the
statements in the correct order in your book
Carbon dioxide levels rise due to
pollution Global warming starts
- weather patterns are
affected
Life begins in the oceans. Simple plants
called cyanobacteria use carbon dioxide
in photosynthesis. Ozone forms and
oxygen levels start to rise
Earth is a ball of molten rock,
No atmosphere is present
Land plants start to appear
Oxygen levels rise rapidly
Earth starts to cool down. Water
vapour begins to condense and oceans
are formed
Earth is still too hot for any
surface water Its surface
is covered in volcanoes
Animals evolve due to the
increase in oxygen
Balance between carbon dioxide
and oxygen is achieved

assuming that your periodic table has eighteen columns, you should highlight   the four elements in the third column from the left of the table.

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the have energy higher than those in the orbital while lower than those of the orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the orbital is therefore filled right after orbitals and before orbitals.  

potassium has electron configuration and calcium . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the and should be highlighted as well.

fe 55.85 g/mol and h2o 18.02 g/mol.