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Summary of the Atom atoms are the smallest particles that can be uniquely associated with an element Atoms cannot break down further by chemical means.

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Presentation on theme: "Summary of the Atom atoms are the smallest particles that can be uniquely associated with an element Atoms cannot break down further by chemical means."— Presentation transcript:

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2 Summary of the Atom atoms are the smallest particles that can be uniquely associated with an element Atoms cannot break down further by chemical means. each element has unique atoms atoms are composed of e -, p and n atoms are electrically neutral (# of e - = # of p) for a single element, isotopes differ only in number of n (neutrons) atoms have characteristic masses (atomic weights) atoms combine with one another in definite, whole number proportions to make compounds

3 ~ m nucleus Mass 9 x kg Mass > kg electron

4 ~ 1 – 7 x m (1 – 7 fermi)

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6 atoms are dominantly empty space: If an oxygen atom had a total radius of 100 km, the nucleus would be a ~1 m diameter sphere in the middle. electron orbits The Spacious Atom

7 In a simplistic model, electrons float around the nucleus in energy levels called shells. As the number of electrons increases, they start to fill shells farther out from the nucleus. In most cases, electrons are lost or gained only from the outermost shell. electron orbits Electrons in Orbit

8 Atom Nucleus

9 Most of the atom is… empty space!

10 The Nuclear Model of the atom

11 Mass of an electron is approximately 1/1840 th of a proton or neutron. Mass of a neutron is very close to the mass of a proton. 1 atomic mass unit (amu or u)= x g 1 g= x10 23 amu amu is defined by assigning a mass of exactly 12 amu to an atom of C-12 isotope.

12 1 amu (atomic mass unit) is… 1/12 th of the mass of one carbon-12 atom.

13 Most of the mass of the atom is… formed by the nucleus.

14 Subatomic Particles ParticleSymbol Charge Relative Mass(unit) Electron e Proton p Neutron n0 1

15 Atomic Number, Z (nuclear charge) 11 Na Atomic Number Symbol is the total number of protons in the atom. Atoms are identified by their proton numbers.

16 All atoms of an element have the same number of protons 11 Na 11 protons Sodium

17 Number of Electrons If an atom is neutral ; The net charge on the atom is zero Number of protons = Number of electrons Atomic number = Number of electrons in a neutral atom

18 Ions have a net electrical charge since the total number of electrons isnt equal to the number of protons. can be anions (e - >p + ;formed as a result of gaining electrons; negatively charged), cations (p + >e - ;formed as a result of losing electrons; positively charged). e - + q(charge of the ion) = proton number

19 In chemical rxns, atoms never gain or lose protons. Its the interaction of electrons.

20 Mass Number, A (nucleon number) Counts the number of protons and neutrons in an atom A= p + + n 0 Protons and neutrons (together) are callednucleons.

21 Atomic Symbols Show the mass number and atomic number Give the symbol of the element 23 Na 11 (Z)atomic number (A)mass number sodium-23

22 Notation for Atoms 12 C 13 C C only one isotope of carbon all isotopes of carbon only one isotope of carbon

23 Basic Definitions atomic number = number of protons in the nucleus; mass number = sum of protons + neutrons in the nucleus isotopic mass = mass of a single isotope

24 More Atomic Symbols O P Zn p + 15 p + 30 p + 8 n16 n35 n 8 e - 15 e - 30 e -

25 Learning check For the ion find a)Nuclear charge b)Mass number c)Electron number d)Neutron number

26 Learning check a)Find the value of unknown quantities in the table given below. b) Classify each particle, X, Y, and Z as Cation, Anion and Neutral atom.

27 Homework! Prepare the flash cards having the symbol of the atom on one side and the name on the other side for the first 20 elements on Page 33 in your textbook.

28 Isotopes Atoms with the same number of protons, but different numbers of neutrons. Atoms of the same element (same atomic number) with different mass numbers Isotopes of chlorine 35 Cl 37 Cl17 chlorine - 35 chlorine - 37

29 Isotopes of Hydrogen element has the biggest abundance in nature.

30 Learning Check 1 An atom of zinc has a mass number of 65. A.Number of protons in the zinc atom 1) 302) 353) 65 B.Number of neutrons in the zinc atom 1) 302) 353) 65 C. What is the mass number of a zinc isotope with 37 neutrons? 1) 372) 653) 67

31 Solution An atom of zinc has a mass number of 65. A.Number of protons in the zinc atom 1) 30 B.Number of neutrons in the zinc atom 2) 35 C. What is the mass number of a zinc isotope with 37 neutrons? 3) 67

32 Learning Check 2 Write the atomic symbols for atoms with the following: A. 8 p +, 8 n, 8 e - ___________ B.17p +, 20n, 17e - ___________ C. 47p +, 60 n, 47 e - ___________

33 Solution 16 O A. 8 p +, 8 n, 8 e - 8 B.17p +, 20n, 17e - 37 Cl 17 C. 47p +, 60 n, 47 e Ag 47

34 Learning Check 3 An atom has 14 protons and 20 neutrons. A.Its atomic number is 1) 142) 163) 34 B. Its mass number is 1) 142) 163) 34 C. The element is 1) Si2) Ca3) Se D.Another isotope of this element is 1) 34 X 2) 34 X 3) 36 X

35 Solution An atom has 14 protons and 20 neutrons. A.It has atomic number 1) 14 B. It has a mass number of 3) 34 C. The element is 1) Si D.Another isotope of this element would be 3) 36 X 14


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