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Chemistry Ch. 4
| Question | Answer |
|---|---|
| Who was Democritus? What did he do? | A Greek Philosopher. -The first to suggest the existence of atoms. He reasoned atoms were indivisible and indestructible. |
| Why wasn't Democritus's idea consider a theory? | It lacked experimental support because Democritus's approach was not based on the scientific method. |
| Who was John Dalton? What did he do? | An English chemist and schoolteacher. -Using experimental methods, Dalton transformed Democritus's ideas on atoms into a scientific theory. He formulated hypotheses and theories to explain his observations. |
| What did Dalton's atomic theory state? (1/2) | 1.) All elements are composed of tiny indivisible particles called atoms. 2.) Atoms of the same element are identical. The atoms of any one element are different from those of any other element. |
| What did Dalton's atomic theory state? (2/2) | 3.) Atoms of different elements can mix together or can chemically combine in simple whole-number ratios to form compounds. 4.) Chemical reactions occur when atoms are separated from each other, joined, or rearranged in a different combination. |
| What instruments are used to observe individual atoms? | Despite their small size, individual atoms are observable with instruments such as scanning electron microscopes. |
| What does the radii of most atoms fall within? | 5x10^-11 m to 2x10^-10 m. |
| How do electron microscopes work? | A beam of electrons is focused on the sample. They are capable of much higher magnifications than light microscopes. |
| With the help of electron microscopes, individual atoms can even... | Be moved around and arranged in patterns. |
| What are three kinds of subatomic particles? | Protons, electrons, and neutrons. |
| Who discovered the electron? | J.J. Thomson. |
| What are electrons? | Negatively charged subatomic particles. |
| What was used to discover the electron? | The cathode ray. |
| Thomson, using the cathode ray, knew that the cathode rays were... | Negatively charged because the negative plates repelled it. |
| Who was Robert A. Millikan? What did he discover? | A U.S. physicist. -He carried out experiments to find the quantity of an electron's charge. He found the mass of the electron. |
| What is the mass of the electron, proton, and neutron? | Electron- 9.11 x 10^-28. Proton- 1.67 x 10^-24. Neutron- 1.67 x 10^-24. |
| What are the first three simple ideas about matter and electric charges? | 1.) Atoms have no net electric charge, 2.) electric charges are carried by particles of matter, 3.) Electric charges exist in whole-number multiples of a single basic unit; no fractions. |
| What is the other simple idea about matter and electric charges? | 4.) Negatively charged particles+an equal number of positive particles=an electrically neutral particle. |
| What is a proton? | A positively charged subatomic particle. |
| Who discovered protons? | Eugen Goldstein. |
| Who discovered neutrons? | James Chadwick. |
| What are neutrons? | Subatomic particles with no charge but a mass nearly equal to that of a proton. |
| Who held the Gold-Foil experiment? What did it prove? | Ernest Rutherford. -The atom is mostly empty space. All the positive charge and almost all the mass are concentrated in a small region. He called this region the nucleus. |
| What is the nucleus? | The tiny central core of an atom that is composed of protons and neutrons. |
| How can you describe the structure of the nuclear atom? | The protons and neutrons are located in the positively charged nucleus. The electrons are distributed around the nucleus and occupy almost all the volume of the atom. |
| What makes one element different from another? | Elements are different because they contain different numbers of protons. |
| What is an atomic number? | The number of protons in the nucleus of an atom of that element. |
| Most of the mass of an atom is concentrated in its ________ and depends on the... | Nucleus. -Number of protons and neutrons. |
| What is mass number? | The total number of protons and neutrons in an atom. |
| How do subscripts for elements work? | (Mass Number *over, don't divide* Atomic Number)Symbol |
| What are isotopes? | Atoms that have the same number of protons but different numbers of neutrons. |
| How do isotopes of an element differ? | Because isotopes of an element have different numbers of neutrons, they also have different mass numbers. |
| The isotope of carbon has been assigned a mass of exactly... It also has __ protons and __ neutrons. | 12 atomic mass units. 6;6. |
| What is atomic mass unit (amu)? | 1/12 of the mas of a carbon 12 atom. |
| What is atomic mass? | The weighted average mass of the atoms of an element in a naturally occurring sample of the element. |
| A weighted average mass reflects both... | The mass and relative abundance of the isotopes as they occur in nature. |
| How do you calculate the atomic mass of an element? | To calculate the atomic mass of an element, multiply the mass of each isotope by its natural abundance, expressed as a decimal, then add the products. |
Created by:
OliviaRoark
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