Chemistry Flashcards
What is a proton?
A proton has a positive charge and mass around 1amu
What is a neutron?
A neutron has no charge and mass around 1 amu
What is an electron?
Electron has a negative charge and negligible mass
What does the nucleus contain?
The nucleus contains the protons and neutrons, while the electrons move around the nucleus
What is the atomic number?
The atomic number is the number of protons in a given element
What is the mass number?
The mass number is the sum of an element’s protons and neutrons
What is atomic mass? How does it compare to the mass number?
Atomic mass is essentially equal to the mass number, the sum of an element’s protons and neutrons
What are isotopes?
Isotopes are atoms of a given element (same atomic number) that have different mass numbers. They differ in number of neutrons
How are most isotopes identified?
Most isotopes are identified by the element followed by the mass number (such as carbon-12, carbon-13, and carbon-14)
What are the isotopes of hydrogen named?
The three isotopes of hydrogen go by different names, protium, deuterium, and tritium
What is atomic weight?
Atomic weight is the weighted average of the naturally occurring isotopes of an element. The periodic table lists atomic weights, not atomic masses
What did Rutherford postulate?
Rutherford first postulated that the atom had a dense, positively charged nucleus that made up only a small fraction of the volume of the atom
What does the Bohr model of the atom say?
In the Bohr model of the atom, a dense, positively charged nucleus is surrounded by electrons revolving around the nucleus in orbits with distinct energy levels
What is a quantum?
The energy difference between energy levels is called a quantum, first described by Planck
What is quantization?
Quantization means that there is not an infinite range of energy levels available to an electron; electrons can exist only at certain energy levels. The energy of an electron increases the farther it is from the nucleus
How does an electron jump from one energy to another?
The atomic absorption spectrum of an element is unique; for an electron to jump from a lower energy level to a high one, it must absorb an amount of energy precisely equal to the energy difference between the two levels
What occurs when an electron returns from an excited state?
When electrons return from the excited state to the ground state, they emit an amount of energy that is exactly equal to the energy difference between the two levels; every element has a characteristic atomic emission spectrum, and sometimes the electromagnetic energy emitted corresponds to a frequency in the visible light range
What does the quantum mechanical model posit?
The quantum mechanical model posits that electron do not travel in defined orbits but rather are localized in orbitals; an orbital is a region of space around the nucleus defined by the probability of finding an electron in that region of space
