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4.2 The Structure of an Atom Properties of subatomic particles Protons Electrons Neutrons Comparing subatomic particles –Mention location, mass, and charge.

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Presentation on theme: "4.2 The Structure of an Atom Properties of subatomic particles Protons Electrons Neutrons Comparing subatomic particles –Mention location, mass, and charge."— Presentation transcript:

1 4.2 The Structure of an Atom Properties of subatomic particles Protons Electrons Neutrons Comparing subatomic particles –Mention location, mass, and charge of all. Atomic number and mass –What are they –How are they different –What do they tell us about the subatomic particles Isotopes –Explain and give examples

2 4.2 The Structure of an Atom This 45-foot-tall steel sculpture is made of 10 tons of steel. If a proton had the same mass as the sculpture, then an electron would have a mass of about 5 kilograms.

3 4.2 The Structure of an Atom I.The Structure of an Atom A.Properties of Subatomic Particles 1.Protons- a positively charged subatomic particle that is found in the nucleus of an atom. a.Each proton is assigned a charge of 1+. b.Each nucleus must contain at least one proton. c.Rutherford concluded that the amount of positive charge varies among elements.

4 4.2 The Structure of an Atom 2.Electrons- a negatively charged subatomic particle that is found in the space outside the nucleus. a.Each electron has a charge of 1 . b.Thomson detected the particles that were later named electrons.

5 4.2 The Structure of an Atom 3.Neutrons- a neutral subatomic particle that is found in the nucleus of an atom a.It has a mass almost exactly equal to that of a proton b.James Chadwick is a scientist that concluded that the particles he produced were neutral because a charged object did not deflect their paths.

6 4.2 The Structure of an Atom Everything scientists know about subatomic particles is based on how the particles behave in experiments. Scientists still do not have an instrument that can show the inside of an atom. Comparing Subatomic Particles

7 4.2 The Structure of an Atom 1.Protons, electrons, and neutrons can be distinguished by mass, charge, and location in an atom. 2.Protons and neutrons have almost the same mass. About 2000 electrons equal the mass of one proton. 3.An electron has a charge that is equal in size to, but the opposite of, the charge of a proton. Neutrons have no charge. 4.Protons and neutrons are found in the nucleus. Electrons are found in the space outside the nucleus. B.Comparing Subatomic Particles

8 4.2 The Structure of an Atom 19 K Potassium Atomic Number Atomic Mass Element symbol

9 4.2 The Structure of an Atom C.Atomic Number and Mass Number 1.Atomic Number- the number of protons in an atom of that element. a.All atoms of any given element have the same atomic number. 1)Each hydrogen atom has one proton in its nucleus. 2)Hydrogen is assigned the atomic number 1. b.Each element has a unique atomic number. c.Atoms of different elements have different atomic numbers.

10 4.2 The Structure of an Atom Atomic Number and Mass Number Each element has a different atomic number. A The atomic number of sulfur (S) is 16. B The atomic number of iron (Fe) is 26. C The atomic number of silver (Ag) is 47.

11 4.2 The Structure of an Atom 2.Atoms are neutral, so each positive charge in an atom is balanced by a negative charge. That means the atomic number of an element also equals the number of electrons in an atom of that element. a.Hydrogen has an atomic number of 1, so a hydrogen atom has 1 electron. b.Sulfur has an atomic number of 16, so a sulfur atom has 16 electrons.

12 4.2 The Structure of an Atom 3.Mass Number- the sum of the protons and neutrons in the nucleus of that atom. a.To find the number of neutrons in an atom, you need the mass number of the atom and its atomic number.

13 4.2 The Structure of an Atom REVIEW OF Information found on the PERIODIC TABLE Atomic number tells us # of protons. The atomic number also tells us # of electrons. Atomic mass tells us the # of protons + # of neutrons –(protons + neutrons = atomic mass) OR –(Atomic mass – Atomic Number = neutrons)

14 4.2 The Structure of an Atom What is the atomic number of aluminum? 13 What is the atomic mass of aluminum? 27 How many protons? 13 How many neutrons? 14

15 4.2 The Structure of an Atom D.Isotopes -atoms of the same element that have different numbers of neutrons and different mass numbers. a.To distinguish one isotope from another, the isotopes are referred by their mass numbers. 1) For example, oxygen has 3 isotopes: oxygen-16, oxygen-17, and oxygen-18. All three oxygen isotopes can react with hydrogen to form water or combine with iron to form rust.

16 4.2 The Structure of an Atom Isotopes With most elements, it is hard to notice any differences in the physical or chemical properties of their isotopes. Hydrogen is an exception. Hydrogen-1 has no neutrons. (Almost all hydrogen is hydrogen-1.) Hydrogen-2 has one neutron, and hydrogen-3 has two neutrons. Because a hydrogen-1 atom has only one proton, adding a neutron doubles its mass.

17 4.2 The Structure of an Atom Isotopes Water that contains hydrogen-2 atoms in place of hydrogen-1 atoms is called heavy water. Hydrogen- 2 atoms have twice the mass of hydrogen-1 atoms, so the properties of heavy water are different from the properties of ordinary water.

18 4.2 The Structure of an Atom Assessment Questions 1.In which way do isotopes of an element differ? a.number of electrons in the atom b.number of protons in the atom c.number of neutrons in the atom d.net charge of the atom

19 4.2 The Structure of an Atom Assessment Questions 1.In which way do isotopes of an element differ? a.number of electrons in the atom b.number of protons in the atom c.number of neutrons in the atom d.net charge of the atom ANS:C

20 4.2 The Structure of an Atom Assessment Questions 1.Of the three subatomic particles that form the atom, the one with the smallest mass is the neutron. True False

21 4.2 The Structure of an Atom Assessment Questions 1.Of the three subatomic particles that form the atom, the one with the smallest mass is the neutron. True False ANS:F, electron


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