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Download Name: Chemistry Notes: Chapter 1.1
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Name: ________________ Chemistry What is matter? What is an element? What is an atom? What makes up an atom? How do charged particles interact? What is the structure of an atom? What is the relationship between a proton and a neutron? How big is an atom? What is special about electrons? How do atoms stay together? What are neutral atoms? What is an atomic number? What is an atomic mass number? What is an isotope? (D12) How do we show that something is an isotope? (D13) Notes: Chapter 1.1 Matter is anything that has mass and volume . It can be a s olid , liquid , or gas . A substance that is made of atoms of the same type. Each element is made of a different type of atom. There are over 1 00 known naturally occurring elements. The smallest particle that makes up any type of e lement . All matter is made of atoms. Atoms are very very small. An atom is made up of 3 charged particles: 1. Protons—have a positive (+) charge 2. Neutrons—have no (o) charge (think: neutral) 3. Electrons—have a negative (-) charge Particles with the same type of charge r epel each other—they push away from each other. Particles with different/opposite charges attract each other—they are drawn toward one another. (This is where the saying “opposites attract” came from.) ● The p rotons and neutrons are grouped together in the center of the atom. ● The center of the atom is called the n ucleus . ● Electrons move around o utside the nucleus in what we call an e lectron cloud. ● The nucleus has an overall p ositive charge (because it contains p rotons ). ● The electron cloud has a n egative charge (because it contains electrons) . A neutron has about the same mass as a proton. They are grouped together in the nucleus . Atoms are extremely small . The electron cloud is about 1 0,000 times the size of the nucleus . ● Electrons are much smaller than p rotons (2000 times smaller). ● Electrons move around the n ucleus very quickly. Scientists have found that it is not possible to determine the exact position of any single electron in an atom because they are moving too fast . This is why we picture electrons as a cloud around the n ucleus . Atoms do not have a shell or anything else separating them from the rest of the world. The negatively charged e lectrons are attracted to the positively charged protons . However, electrical c harges that are alike (such as two n egative charges) repel each other. This is why electrons remain s pread out in the electron cloud. Atoms that have no overall electrical c harge because they have an equal number of p rotons and electrons . The atomic number is the number of protons in the nucleus of an atom. This determines the identity (type) of the atom. Example: Oxygen has an atomic number of 8 , while Carbon has an atomic number of 6 . This means that Oxygen has 8 protons, and Carbon has 6 protons. Atomic mass number is the total number of p rotons AND neutrons in the nucleus. Atoms of the same element will always have the same number of protons , but may have different numbers of n eutrons . Isotopes are atoms of the same element that have a d ifferent number of neutrons . Some elements have m any isotopes, while other only have a f ew. An isotope is described by the name of the element and the total number of its protons and neutrons (atomic mass number). Ex: Chlorine-35 (name-atomic mass number) What is an ion? (D14) How is an ion formed? (D14) How do we show that something is an ion? How do I find the number of protons in an atom? How do I find the number of neutrons in an atom? How do I find the number of electrons in an atom? An ion is an atom that has an electric charge . The charge can be p ositive or negative . Ions have d ifferent numbers of protons and e lectrons . An ion is formed when an atom g ains or l oses one or more e lectrons. An ion is described by its name (or symbol) and c harge. Ex: Oxygen (-2) or O2 # protons = Atomic # (the number above the element’s symbol on the periodic table) Atomic mass number minus (-) the number of protons ● ● In a neutral atom, the # of e lectrons is the same as the number of p rotons. In an ion (with a positive or negative charge), the number of electrons is different from the number of protons. To find the number of electrons, subtract the charge from the number of p rotons the atom has o # protons – charge = # electrons Questions: 1. What particles are found in the nucleus of an atom? ________________________________ 2. What particles move around outside the nucleus? __________________________________ 3. If all atoms are composed of the same particles, how can there be more than 100 different elements? _____________________________________________________________________ ______________________________________________________________________________ 4. Why do electrons stay in an electron cloud around the nucleus? _____________________ _____________________________________________________________________________ 5. What particles are counted to determine the atomic number? ________________________ 6. Use your knowledge of atomic numbers to fill in the chart below. If an atom is an ion, I have written its charge in parenthesis after the element name. Ex: Oxygen (-2) has a charge of -2. Element Atomic Number Atomic Mass # # Protons # Neutrons # Electrons Hydrogen (+1) Oxygen (-2) 1 8 16 Carbon-12 12 6 Carbon-14 14 6 Gold 79 Iron 26 Nitrogen (+3) 1 197 30 14 7 7. Which of the elements in the table above are ions? _________________________________________ 8. Which of the elements in the table above are isotopes? _____________________________________ 9. What particles are counted to determine the atomic mass number? __________________________ 10. If oxygen has 8 protons and 8 neutrons, what is its atomic mass number? ____________________ 11. Why do you think neutrons are necessary in the nucleus of an atom? 12. Draw a picture of an atom:
