233760
| Questão | Responda |
| what does an element contain? | all the same type of atoms |
| what is group 1 of the periodic table? | the alkali metals |
| what are the properties of an alkali metal? | soft cut with knife, low densities float on water. react H20 metal hydroxide hydrogen. |
| how many elements exist? | more than one hundred |
| state symbols | (g)=gas (l)=liquid (s)=solid (aq)=aqueous solution |
| what do halogens consist of? | diatomic molecules (molecules made of 2 atoms) |
| what is an important thing to note? | a more reactive halogen will displace a less reactive halogen from its compound |
| Who arranged the modern periodic table? | Dmitri Mendeleev |
| what happens to elements when they are heated? | they emit coloured flames |
| what is inside an atom? | a tiny,central nucleus that contains protons and neutrons |
| how is the modern periodic table arranged? | in order of proton number number of protons+number of neutrons=relative atomic mass |
| how are electrons arranged? | in shells around the nucleus first shell-holds 2 electrons 2nd-8 electrons,3rd-8 |
| what are the alkali metals? | lithium(Li),sodium(Na),potassium(K),rubidium(Rb), caesium(Cs) and Francium(Fr) |
| what are the halogens? | group 7 of the periodic table |
| What are examples of halogens? | chlorine-pale green gas-pale green bromine-red-brown liquid-reddish brown. iodine-dark grey-purple |
| what do group 7 elements need? | they are corrosive and toxic so you need a fume cupboard when handling them |
| what are ionic compounds? | compounds of a group 1 element and a group 7 element (e.g sodium chloride are solids with high melting points) |
| why are they ionic compounds? | they contain charged particles,or ions, that are arranged in a regular pattern called a crystal lattice |
| what are properties of ionic compounds? | they are soluble in water and conduct electricity when they are melted. ions are free to move when crystals dissolved. |
| when do positive and negative ions form? | positive ions form when atoms lose outer-shell electrons negative ions form when atoms gain outer shell electrons |
| some chemical elements | H(Hydrogen) C(Carbon) O2(Oxygen) |
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