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Holt Chem Chapter 3
| Term | Definition |
|---|---|
| law of definite proportion | a chemical compound always contains the same elements in exactly the same proportions by mass |
| law of conservation of mass | mass cannot be created or destroyed in ordinary physical and chemical changes |
| law of multiple proportions | when two elements combine to form two or more compounds, the mass of one element that combines with a given mass of the other is in the ratio of small whole numbers |
| electron | subatomic particle with a negative charge that is NOT found in the nucleus of the atom |
| nucleus | an atom's central region, which is made up of protons and neutrons |
| proton | a subatomic particle that has a positive charge and is found in the nucleus of the atom; the particle that determines the identity of the atom and is indicated by the atomic number. |
| neutron | a subatomic particle that has a negative charge and is found in the nucleus of the atom. |
| atomic number | the number of protons in the nucleus of an atom |
| mass number | the sum of the number of protons and neutrons in the nucleus of an atom |
| isotope | an atom that has the same number of protons as other atoms of the same element but has a different number of neutrons; The atomic number is the same as other atoms from that same element but the mass number is different. |
| orbital | a region in an atom where there is a high probability of finding electrons |
| electromagnetic spectrum | all the frequencies of wavelengths of electromagnetic radiation |
| ground state | lowest energy state |
| exited state | a state in which an electron has more energy than it does at its ground state |
| quantum number | a number that specifies the properties of electrons |
| Pauli Exclusion Principle | two particles of a certain class cannot be in the same energy state |
| electron configuration | the arrangement of electrons in an atom |
| auffbau principle | the structure of each successive element is obtained by adding one proton to the nucleus of the atom and one electron to the lowest-energy orbital that is available |
| Hund's rule | for an atom in the ground state, the number of unpaired electrons is the maximum possible and the unpaired electrons have the same spin. |
| atomic mass | the average mass of an atom represented in amu (atomic mass units); This is mostly a number with a decimal because it is the average of all the isotopes for that element. |
| mole | SI unit for the amount of a substance whose number of particles is the same as the number of atoms in 12 grams of Carbon 12 |
| molar mass | the mass in grams of 1 mole of a substance |
| Avogadro's number | 6.022 x 10^23 ; this is the number that is equal to one mole |
| Dalton's First Principle (T or F) | 1. all matter is composed of extremely small particles called atoms, which cannot be subdivided, created, or destroyed; False |
| Dalton's Second Principle (T or F) | 2. atoms of the same element are identical in physical and chemical properties; False |
| Dalton's Third Principle (T or F) | 3. atoms of different elements differ in their physical and chemical properties; True |
| Dalton's Fourth Principle (T or F) | 4. atoms of different elements combine in simple, whole-number ratios to form compounds; True |
| Dalton's Fifth Principle (T or F) | 5. in chemical reactions atoms are combined, separated, or rearranged but never created, destroyed, or changes;True |
| Do electrons have mass? | Yes, but the mass is very tiny, only about 1/1836 of the proton |
| Do protons or neutrons have more mass? | a neutron has slightly more mass than a proton |
| How does distance affect the amount of force? | The smaller the distance between two charges the greater the force between them. |
| How do you find the number of protons in an atom? | The atomic number gives the number of protons. |
| How do you find the number of electrons in an atom? | The number of electrons in an UNCHARGED atom (not an ion) is equal to the number of protons; The number of protons is given by the atomic number. |
| How do you find the number of neutrons in an atom? | You subtract the atomic number (# protons) from the mass number (sum of # protons and neutrons); mass number - atomic number = number of neutrons |
| Why must there be an attractive force to explain the existence of stable nuclei? | Protons are highly charged and very close to one another in the nucleus; the force of repulsion between protons is strong. There must be an attractive force which can overcome the repulsive force in order to stabilize the nuclei and keep it together. |
| What is the photoelectric effect? | When light is above a certain frequency and it hits a metal, the metal will emit electrons. |
| What does it tell scientists? | The fact that light had to be above a certain frequency meant that light was not just a wave but also "packets" of energy called photons. This was the beginning of the quantum model of the atom. |
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