Atoms, Elements, Compounds, Mixtures

• What is the radius of an atom? 0.1 nanometer (1x10-10 meters)
• Which model of the atom do chemists use? The nuclear model
• Describe the nuclear model of the atom?

  An atom has a small central nucleus that is orbited by electrons
• What chrage does a neutron have? No charge
• What is an atom mostly comprised of? The nucleas is only 1/10 000 the size of the atom. An atom is mostly empty space
• What is an electron shell? A path on which an electron moves around the nucleus
• Where is most of the mass located in an atom and why is this? Most of the mass in an atom is located in the central nucleus. This is because electrons have virtually no mass
• What is the relative mass of a proton? 1
• What is the relative mass of a neutron? 1
• What is the relative mass of an electron? very small
• What is the relative charge of an electron? -1
• what is the relative charge of a proton? +1
• what is the relative charge of a neutron? 0
• Explain why atoms are uncharged particles Atoms have the same number of protons (+1) and electrons (-1) so the charges balance out to no overall charge
• What is an ion? An atom that has lost o gained electrons and therefore has become charged
• What is the overall charge of an ion with 2 more electrons than protons? 2-
• What is the overall charge of an ion that has lost 3 electrons? 3+
• What is the relative size of the nucleus compared to the rest of the atom? The nuclues occupies about 1/10 000 of the space in the atom
• What determines what element an atom is? The number of protons in its nucleus
• What must a substance be for it to be an element? It must be wholy made of only one type of atom
• How many known elements are there? There are 118 known elements
• What two things do atoms of the same element have in common? Number of protonsAnd therefore number of electrons as atoms are nuetrally charged
• What are the two numbers depicted in a nuclear symbol? atomic numbermass number
• How can you tell which number is the atomic number on a nuclear symbol? The atomic number is the smaller number on the bottom
• How can you tell which number is the mass number on a nuclear symbol? the mass number is the bigger number on the top
• What is the atomic number? The atomic number is the number of protons (and therefore electrons) in the atom
• What two things does the atomic number tell you? Number of protonsNumber of electrons
• What is the mass number? The total number of protons and neutrons
• How do you work out the number of neutrons in an element using its nuclear symbol? Mass number - Atomic number
• How do you work out the number of electrons in an atom from its atomic number and mass number The number of electrons is equal to the atomic number
• What is an isotope? An isotope is a different form of the same element which has the same number of protons but a different number of neutrons
• How does an isotope's nuclear symbol differ from the normal element's? It has the same atomic number but a different mass number
• What is relative atomic mass (Ar)? The average mass, taking into account the different masses of different isotopes of an element and how abundant they are
• Why are some mass numbers decimal numbers on the periodic table? Ar, relative atomic mass is used as the mass number on the periodic table
• How do you calculate the relative atomic mass of an element? Ar = sum of (isotope abundance x isotope mass number) / sum of abundances of all the isotopes
• What is a compound? A compound is a substance formed from two or more elements in fixed proportions throughout the compund and are held together by chemical bonds
• How are compounds made? When elements react together
• How are compounds represented? By formulae
• How are the properties of a compound related to the properties of the original elements? The properties of a compound are completly different from the properties of the original elements
• What cannot be used to seperate compounds? Physical methods and processes