7  A layer of negatively charged particles surrounding an atom. (8,5)

 8  About halfway between the bow and the stern. (8)

 9  Small, cheese-addicted mammals. (4)

10 Element with the symbol Hg. (7)

12 A genetically identical copy. (5)

14 Group of organic compounds of which lactose and glucose are members. (5)

16 Type of cage used to isolate things from all electromagnetic interference. (7)

19 An optical effect produced by light interacting with ice crystals in the atmosphere. An iconic Xbox game. (4)

20 Dissolve the maximum mass of solute into a solvent at a given temperature. (8)

22 Mendeleev's list of elements, improved by Moseley. (8,5)

 2  Having a pH below seven. (6)

 3  A grove of fruit trees. (7)

 4  Single Nucleotide Polymorphisms. (5)

 5  Antiseptic chemical used in Ancient Egypt for embalming, found in thyme. (6)

 6  The interface between a fetus and its mother. (8)

11 Enlightened, cultivated, what we hope you will become! (8)

13 A regular spacing or arrangement of particles within a material e.g. diamond. (7)

15 Bomb or Kitten! (6)

17 Trachea. (6)

18 Detached; a stage whisper. (5)

21 Hydrated magneisum silicate, and an ingredient in baby powder. (4)