Chapter 7: Atomic Theory—Inside the Invisible Flashcards
What are the three parts of an atom?
Protons, neutrons, and electrons; protons have positive charges; neutrons have no charges; electrons have negative charges. Protons and neutrons make up the nucleus while the electrons orbit them.
What are molecules?
Two or more kinds of non-metallic atoms combined (*combinations of metal and non-metal atoms are technically not molecules). They are the smallest parts of a compound. Molecules are formed when atoms share electrons. Both elements and compounds can be composed of molecules.
What was the First Scientific Atomic Theory?
It was proposed by John Dalton, and suggested that all matter was composed of atoms. However, these atoms were envisioned as smooth solid spheres, and they had no electric charges. All atoms of one element were identical, and each kind of atom had a particular mass. These atoms could combine to form compounds with certain ratios.
What change did Michael Faraday make to John Dalton’s theory?
He discovered that atoms could gain electric charges. Like charges repelled and opposite charges attracted.
What revisions did J.J. Thomson make to the Atomic Theory?
He found out that atoms contained electrons and that charges were gained by removing or adding them. He said that atoms were mostly positive, with the exception of electrons, which were scattered randomly throughout the atom. His atomic model resembled a raisin bun.
What revisions did Ernest Rutherford make to the Atomic Theory?
He discovered that there was a nucleus by performing an experiment in which he shot positively charged particles at a thin sheet of gold. A majority of the particles passed straight through the gold, but some bounced off. He concluded that most of an atom consisted of empty space, and the mass was concentrated in the center (the nucleus), while the electrons orbited it. He discovered the remaining of the three subatomic particles, the proton and the neutron.
What is the nucleus of an atom made of?
It is made of protons and neutrons.
What do neutrons contribute to the atom?
They hold the nucleus together, as opposite charges attract. That way, the protons do not separate and cause the atom to fall apart, because they all have positive charges.
What is the emission spectrum?
It is the pattern of wavelengths or colours of light an element emits when its atoms absorb electrical or heat energy. Each element emits its own pattern.
What revisions did Niels Bohr make to the Atomic Theory?
He proposed the theory that electrons were arranged to orbit in ‘shells’. The amount of energy they had depended on how far they were from the nucleus (the farther an electron was, the more energy it had). He also proposed that atoms always wanted full shells of electrons.
According to the Atomic Theory of Matter, how many electrons can be in each shell?
The first shell can only have 2, the second 8, the third 8, and the fourth 18.
What is the atomic number of an atom?
The amount of protons, and it helps determine the order of elements in the Periodic Table of Elements.
What is the atomic mass of an atom?
The total number of protons and neutrons in the nucleus of an atom.
What is an ion?
A charged atom. Ions can be either positive or negative. The charge of an ion is called the ion charge.
How is standard atomic notation written?
- element symbol in the middle (or right, depending on if the atom has a charge)
- atomic mass and number on the left. The mass number is always above the atomic number.
- If the atom has a charge, the number is placed beside the symbol (*if the charge is 1, the 1 is not usually written).
