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8th grade chemistry
Unit one chemistry
| Question | Answer |
|---|---|
| what is chemistry | the study of :the changes that matter undergoes and the composition of matter |
| what is matter | anything that has mass and takes up space |
| what are atoms | one of the building blocks of matter, |
| what is the size of atom | 10^-10 |
| who was John Dalton | helped with experiments to the acceptance of the idea of an atom |
| What were the 4 main points of Dalton in the universe | 1. all elements are composed of atoms- they are indivisible and indestructible particle. 2. atoms are the same element are exactly alike. 3.atoms are different elements are different. 3. compounds are formed by the joining of atoms of two or more elements |
| what are the elements | a substance that cannot be broken down into a simpler substance by ordinary chemical change. |
| what is the most common element in the universe | hydrogen- 90% |
| what is the most common element in the earth's crust | oxygen- 47% |
| What are proton | positively charged particles- P+ |
| What is proton charge | +1 |
| what are proton relative mass | 2000 |
| where is proton location | nucleus - center of atom |
| what are Neutron definition | uncharged particle-n |
| what is neutron charge | 0 |
| what are neutron relative mass | 2000 |
| what are neutron location | nucleus- center of atom |
| what are electrons | negatively charged particle- equal to the number of proton |
| what is electron charge | -1 |
| what are electron relative mass | 1 |
| what are electrons location | orbits the nucleus in the shell |
| what part of the atom is pulled out and enlarged to show more detail> | nucleus |
| why would it be impossible to show the exact dimensions of an atom on paper | to small to see with human eye- there are a million atoms in just a period. |
| what is atomic number | determines the number of protons in the nucleus |
| what is mass number | the total number of protons and neutrons in an atoms nucleus- not given on the period table (is a whole number) |
| what is atomic mass | total number of protons in an atoms's nucleus and is on the periodic table (may not be a whole number- average) |
| when determining the mass of an atom, the electrons are not considered. why can scientist disregard electrons | electrons has no mass. atomic mass- atomic # = neutrons |
| where do electrons live | in the orbit or shell or energy levels |
| when determining the number of shells an atom has, you should look at the ________ on the periodic table | determined by the table which period (row) it is in. |
| what elements are in the human body | oxygen, carbon, hydrogen, nitrogen, other |
| what is isotopes | are atoms of the same elements that have different number of neutrons than normal. some have many when others have a few. |
| what are valence electrons | an electron that is in the outer most shell of any elements. they are the beginning for compound bonding |
| when determining the number of valence electrons in the outermost shell of an atom, you should look at the ______ on the periodic table | group (column) |
| which group has a full outer most shell | 18 |
| do electrons closer to the nucleus have higher or lower energy? | lower energy closer to the nucleus |
| what is an example of isotope element | carbon, radon, potassium, uranium |
| the atomic number of potassium is 19. How does potassium -39 differ from potassium -41? | neutrons for Potassium 39 is 20 and Potassium 41 is 22. and electrons would be 19 for both |
| when an element is radioactive, it means it has an unstable number of | isotopes |
| what are ions | an atom that has lost or gained one or more electrons and has become charged either positive or negative. does not have an overall electric charge. |
| positive ions | loses electrons |
| negative ions | gains electrons |
| cations | metals losing one or more electrons to form positive ions |
| anions | non-metals tend to gain one or more electrons to form negative ions |
| do negative or positive ions weigh more | stay the same in mass weight, because electrons do not determine weight. |
| compare Magnesium with a 2+ and sodium with a + charge | they would have the same amount of electrons |
| how do you determine whether an element is going to gain or lose ions. | depending if they are 4 or less or 4 or more on the outer shell ring. less than 4 they will lose, 4 or more they will gain. |
| what is the difference between Bohr model | shell 1st-2 electrons, 2nd- up to 8 electrons 3rd- up to 8 electrons |
| what organization model did Mendeleev use? | periodic table |
| what is the periodic table | it shows a periodic or repeating pattern of properties of the elements. left space for new elements to be discovered. |
| where are the metals, metalloid, nonmetal found on the periodic table | most of the metal is the table, with metalloid then non metals (except H is non metal) |
| how is the table organized | by the atoms of the elements - atomic number (atomic mass is on the bottom) |
| group is | the elements in a column- family of elements- usually related the atomic size decrease as it moves from left to right |
| period is | the horizontal row in the table-properties of elements change in a predictable way- atomic size increase when moved down |
| which side of the table are positive ions | left side |
| which side of the table is negative ions | right side |
| would you expect strontium (Sr) to be more like Potassium (K) or Bromine (br) why | more like K because they are closer in groups. to me more like family. they are both positive and metals. where Br is non metal, and negative charge |
| What are some properties that can be related to the periodic table | atomic size, metal, non metal, gaining or losing electrons, density of an element |
| which side of the chart has largest atoms | right side |
| where would the largest atom be on the chart | bottom right side |
| what part of the periodic table is the column labeled group 17 taken | right side |
| from what row labeled period 3 taken | top starting left and going right |
| how many valance electrons do the elements in group 1 have | 1 |
| how many shells do the elements in period 4 have | 4 |
| what are the most common elements | metal |
| what does radioactivity mean | how likely an element will undergo a chemical change |
| what make an element reactive | how their valence electron is incomplete |
| where on earth can you find a noble gases | group 18- because they almost never react with another element |
| how do you organize elements base on reactivity | least to greatest (lithium, silicon, argon |
| which groups of elements (metal or non metals) are reactive | non metals |
| which group of elements metal or non metal can not react with others | metals |
| what is half life | amount of time that it takes for one-half of the atom in a particular sample to decay. characteristic of isotopes and independent of the amount of material. not affected by temperature or pressure. turn into a new element |
| how do you determine half life of an element | need radioactive isotope /# of years |
| what are the 3 main classes of elements on the periodic table | reactive metals transition metals, rare earth metals |
| what are the 3 regions of the periodic table | metal, metalloids and non-metals |
| what is alkali metals | very reactive metal, not found as free element in nature, always bonded |
| what is alkaline metals | less reactive metal, conducts electricity, always combined with non metal, need for food |
| how do you change from standard to scientific notation and back | 2000+10000= 20^6 |
| how can an atom of one element change into an atom of a different element | incomplete valence electron level. atoms will bond until the level is complete calling it radioactivity |
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