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scienceobrien
atoms and compounds
Question | Answer |
---|---|
What are the electrons that are farthest from the nucleus? | valence |
How many valence electrons can an element have? | 1 to 8 |
How many valence electrons make an atom stable? | 0, 2, or 8 |
What makes an atom neutral? | The same number of protons and electrons |
When an atom becomes charged after gaining or losing electrons it becomes an..... | ion |
When an atom loses an electron they have a.... | positively charged |
When an atom gains an electron they become... | negatively charged |
Name two ions | Na and Cl |
Name two chemical bonds. | Ionic and Covalent |
What is an ionic bond? | bond between metals and non metals |
Ionic bonds produce compounds made up of hard crystals and have what kind of melting point? | high |
what ending do you put on the second element in an ionic compound? | ide Ex: Sodium Sulfide |
When does a covalent bond form? | When atoms share valence electrons |
Where do covalent bonds happen? | between nonmetals |
What kind of compounds are produced from ionic bonds? | molecular |
Are molecular compounds poor or good conductors of heat? | poor Ex: H2o |
What is a polar molecule? | a compound with slighlty charged ends |
What is a nonpolar molecule | atoms that pull equally on the electrons |
What is a chemical reaction? | when there is a chemical change in a substance |
What evidence shows us that a chemical change has happened? | color, gas production, temperature, precipatate(liquids mixed to form a solid) |
Substances you start with in a chemical reaction are called | reactants |
The materials you are left with after a chemical reaction are called | products |
What are the 4 types of chemical reactions called? | Exothermic, Endothermic, Synthesis, and Decomposition |
In an exothermic reaction energy is | released |
In an endothermic reaction energy is | absorbed |
Name and example of an exothermic reaction | burning wood |
Name an example of an endothermic reaction | instant ice pack |
What is synthesis? | two or more substances combine to make a complex substance |
What is decomposition? | a complex substance broken down in to simpler substances |
What is the Law of Conservation of Mass? | The amount of matter involved in a chemical reaction does not change. Mass of Reactants=Mass of Products |
What is activation energy? | the amount fo energy needed to get a reaction started |
What is the collision theory? | reactant molecules collide with a certain amount of energy to react and form products |
Catalysts | speed up reactions |
Inhibitors | slow down chemical reactions |