Chemistry crossword

4. group 17 elements in the periodic table;the most reactive non-metals
8. combination of pure substances;unlike a compound,the components of a mixture do not combine chemically and are not always in the same ratio
11. variations within a species
12. the smallest part of an element that is representative of that element;a neutral particle made up of a nucleus containing protons and neutrons,and in which the number of electrons equals the number of protons
14. invisible negatively charged particle that orbits the nucleus of an atom
16. atom that has become electrically charged because it has lost or gained electrons;a positive ion is an atom that has lost one or more electrons;a negative ion is an atom that has gained one or more electrons
17. substance that reacts with another substance or substances in a chemical reaction to create new substances with different properties
19. pure substance that cannot be broken down into other substances;substance made up of only one type of atom
21. positively charged particle in the nucleus of an atom
23. catalyst involved in chemical reactions in living things
24. ability to do work

1. horizontal row of elements in the periodic table
2. positively charged centre of an atom;contains protons and neutrons
3. substance that helps a chemical reaction to proceed more quickly
5. amount of mass in a given volume of a substance
6. element that has both metallic and non-metallic properties
7. chemical reaction that occurs when oxygen reacts with a substance to form a new substance and give off energy
8. shiny,malleable,ductile element that conducts electricity
9. description of a substance that can be pounded or rolled into sheets
10. new substances produced in a chemical reaction between reactants
13. group of atoms joined by covalent bonds
15. chemical combination of two or more elements in a specific ratio
18. neutral particle in a nucleus of an atom
20. organic molecules made up of atoms of carbon,hydrogen and oxygen (ex,fats,oils and waxes);lipids are insoluble in water
22. vertical column of elements in the periodic table;elements in a family all have similar chemical properties;also called a group