Atoms & Isotopes

• What are atoms considered to be in relation to matter?


  Atoms are the building blocks of all matter.
• What is the approximate radius of an atom?


  The radius of an atom is about $1 \times 10^{-10} \text{ m}$.
• How many atoms can fit side by side across a thumbnail?

  About one hundred million atoms can fit side by side across a thumbnail.
• What is located at the center of an atom?


  An atom has a tiny, dense nucleus at its center.
• What particles orbit around the nucleus of an atom?


  Electrons orbit around the nucleus of an atom.
• How does the radius of the nucleus compare to the radius of the whole atom?


  The radius of the nucleus is over 10,000 times smaller than the whole atom.
• What does the nucleus of an atom contain?


  The nucleus contains protons and neutrons.
• What is the charge and relative atomic mass of protons?


  Protons are positively charged particles with a relative atomic mass of one unit.
• What is the charge and relative atomic mass of neutrons?


  Neutrons have no charge and a relative atomic mass of one unit.
• What is the mass of electrons compared to protons or neutrons?


  Electrons have almost no mass, about 1/2000 the mass of a proton or neutron.
• What is the composition of an atom?

  An atom consists of a nucleus (protons and neutrons) and electrons.
• How are electrons arranged in an atom?


  Electrons are arranged in energy levels around the nucleus.
• How many electrons can occupy the first energy level?


  Only two electrons can occupy the first energy level.
• How many electrons can fit in the second and third energy levels?


  Only eight electrons can fit in both the second and third energy levels.
• What happens to electrons in higher energy levels?


  Electrons in higher energy levels have greater potential energy due to their distance from the nucleus.
• What can happen when electrons absorb energy?


  When electrons absorb energy, they can move to a higher energy level.
• What type of objects are good absorbers of radiation?


  Dark colored objects are good absorbers of radiation.
• What occurs when an electron moves back down to its original energy level?


  When an electron moves back down, it emits a wave of electromagnetic radiation.
• What produces all the colors in the visible spectrum?

  All colors in the visible spectrum are produced by electrons moving down energy levels and emitting electromagnetic radiation.
• What is the atomic number of an atom?


  The atomic number is the number of protons in an atom.
• How are elements in the periodic table ordered?


  Elements in the periodic table are ordered by their atomic number.
• What is the atomic number of hydrogen?


  The atomic number of hydrogen is 1.
• What is the atomic number of sodium?


  The atomic number of sodium is 11.
• What is the atomic number of uranium?


  The atomic number of uranium is 92.
• What does the atomic number also equal in an atom?


  The atomic number is also equal to the number of electrons in an atom.
• How can the number of neutrons in an atom be found?


  The number of neutrons can be found by subtracting the atomic number from the mass number.
• If a sodium atom has a mass number of 23 and an atomic number of 11, how many neutrons does it have?

  The number of neutrons is $23 - 11 =$$12$.
• What is nuclear notation?


  Nuclear notation shows the mass number and atomic number of an atom with the atomic symbol.
• In nuclear notation, what does the top number represent?


  The top number in nuclear notation is the mass number.
• In nuclear notation, what does the lower number represent?


  The lower number in nuclear notation is the atomic number.
• How many protons, neutrons, and electrons are in a gold atom with atomic number 79 and mass number 197?


  Gold has 79 protons, 118 neutrons, and 79 electrons.
• What are isotopes?


  Isotopes are atoms of the same element that have an equal number of protons but a different number of neutrons.
• How many isotopes does hydrogen have?


  Hydrogen has three isotopes, each with a different number of neutrons.
• Do isotopes affect the chemical properties of an atom?


  The number of neutrons does not affect the chemical properties of an atom.
• Why is the mass number of chlorine given as 35.5?


  The mass number of chlorine is given as 35.5 because it has two isotopes, one with a mass number of 35 and the other with a mass number of 37.
• Which isotope of chlorine is more abundant?


  Chlorine-35 is about three times more abundant than chlorine-37.
• What remains the same in different isotopes of an element?


  The number of electrons and protons in different isotopes remains the same.
• What can happen to isotopes that are unstable?


  Unstable isotopes can have an imbalance of protons and neutrons.
• How many protons, neutrons, and electrons are in chlorine-35 and chlorine-37?


  Both have 17 protons, chlorine-35 has 18 neutrons, and chlorine-37 has 20 neutrons.
• What happens when electrons are knocked out from an atom?


  When electrons are knocked out, the atom becomes positively charged and is called a positive ion.