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# Science 20

### Stack #15061

Science 20 Qs - Chemestry | Science 20 As - Chemestry |
---|---|

significant digits rule is ... | do not count leading zero's, but do count trailing zero's |

do not add zero's unless they are ... | significant |

put a zero in front of a decimal but _______ count it as significant | do not |

certainty rule is ... | when multiplying or deviding, round the answer to the smallest amount of digits in the question |

precision rule is ... | when adding or subtracting, round the answer to the smallest number of decimal places |

_________the last significant digit in your answer | round off |

do not round off the number until ... | the end of the question |

with scientific notation you ... | move the decimal place so that only one non - zero digit appears to the left of the decimal |

drop all ____________ zero's | non - significant |

multiply this number by 10 coefficient n, where n is... | the number of places the decimal was moved |

when the first digit after thoes retained is less than 5 ... | all digits retained remain the same |

when the first digit after thoes retained is greater than 5 ... | the last digit retained is increased by one |

there are ____ different elements | 109 |

one atom of a particular element is represented by a ... | symbol |

the symbol is either a capital letter by itsself or ... | a capital letter followed by a lower case letter |

the symbol for carbon is ... | C |

the symbol for cobalt is ... | Co |

atoms combine together to form ... | molecules |

a molecules is represented by symbols placed side by side to form ... | formulas |

different kinds of atoms combined together produce ... | a molecule of a compound |

in the formula H2O, the number 2 is called a ________ | subscript |

the subscripts in a formula tell the ______________ in the molecule | number of each kind of atom |

some molecules are made up of two or more ... | atoms of the same element combined together |

elements of the same kind form together when ... | they don't want to be alone (they are unstable and become more stable when paired) |

Dalton's atomic structure ... | invisible and round like billiard balls |

Thompson's atomic structure ... | positive sphere, embedded electrons almost like a raisin bun |

Rutherford's atomic structure .... | small positive neucleus surrounded by electrons |

Bohr's atomic structure .... | certain number of electons in quantisized energy levels |

protons and neutrons are found in the inner core of the atom called ... | the neucleus |

______ are found moving around the outside of the nucleus | electrons |

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Tigger 27