Unit 2/B: Chemical Interactions Chapter 5: Atomic Structure and the Periodic Table Chapter 6: Chemical Bonds and Compounds Chapter 7: Chemical Reactions Chapter 8: Solutions Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Chapter 5: Atomic Structure and the Periodic Table A substance’s atomic structure determines its physical and chemical properties 5.1 Atoms are the smallest form of elements 5.2 Elements make up the periodic table 5.3 The periodic table is a map of the elements Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

5.2 Elements make up the periodic table Before, you learned: Atoms have a structure Every element is made from a different type of atom Now, you will learn: How the periodic table is organized How properties of elements are shown by the periodic table Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Warm-up questions The atomic number of an atom is the number of protons and neutrons in the nucleus Atomic mass number Isotopes are atoms of the same element, but with a different number of neutrons True When an atom gives up an electron, it becomes an ion with a negative charge positive Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Table 1. Characteristics of Some Elements 1. Complete the table below, considering 'normal' atoms only (not ions or isotopes). Table 1. Characteristics of Some Elements What is the atomic weight of the normal oxygen atom? Of the normal argon atom? 3. What is the atomic weight of a hydrogen atom? Of a hydrogen ion? Element # Electrons # Protons # Neutrons hydrogen   1 helium 2 sodium 11 chlorine 17 argon 18 carbon 6 nitrogen 7 oxygen 8 Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Numbers and Mass Numbers All atoms are composed of the same particles… Different numbers of protons in the nucleus Atomic number = # protons in the nucleus Atomic mass number = # protons + # neutrons Same elements have same # protons but not always the same # neutrons, so may have different atomic masses Ex: Chlorine atoms have 17 protons, some have 18 neutrons, some have 20 neutrons = Chlorine isotopes Isotopes: atoms of the same element that have a different number of neutrons Chlorine-35, Chlorine-37 # protons? # neutrons? Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Formation of Positive Ions If the atoms loses one electron, the charges are no longer balanced: one more proton than electrons Size is different: fewer electrons, less repulsion Lose one electron: X+, lose two electrons: X2+ Ex: Na+, Ca2+ Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Formation of Negative Ions If the atoms gain one electron, the charges are no longer balanced: one less proton than electrons Size is different: more electrons, more repulsion Gain one electron: X-, gain two electrons: X2- Ex: Cl-, O2- Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

5.2 Elements make up the periodic table Elements can be organized by similarities Masses Can find the mass of a very large number of atoms of a certain elements and infer the mass of a single one of them Can vary for an element: isotopes “atomic mass” is actually the average mass of all the element’s isotopes Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Mendeleev’s Periodic Table Russian chemist, Dmitri Mendeleev 1860’s – how to organize the elements based on physical and chemical properties? He made cards that contained atomic mass and properties He looked for a relationship between the properties and atomic mass He created a chart: Rows: elements showing similar chemical properties Atomic mass increased by moving down each vertical column 1869 – first periodic table – “periodic” – shows a periodic, or repeating, pattern of properties of the elements Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Predicting New Elements Mendeleev left empty spaces on the table where no known elements fit the pattern Predicted new elements fitting the spaces would eventually be discovered – described their properties! Six years later the “?” after aluminum (Al) was discovered: “gallium In the next 20 years, two others were discovered Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

The periodic table organizes the atoms of the elements by properties and atomic number New table: elements with similar properties are now found in columns, not rows…and atoms are now arranged by atomic number, not mass How to read the periodic table? Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

How to Read the Periodic Table? The number at the top is the atomic number = # protons in the nucleus Chemical symbol - one or two letters; temporary symbols for not-yet named elements have three-letter symbols Name of element number at bottom is the “average atomic mass” of all the isotopes of the elements Color of symbol is the state of matter at room temperature Color of background color of box indicates whether metal, nonmetal, or metalloid (5.3) Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Groups and Periods Elements in a vertical column show similarities in their chemical and physical properties Known as a group Labeled by a number at the top of the column Sometimes a group is called a family of elements because they seem to be related Ex: Group 17 – “Halogen” group Tend to combine easily with other elements and compounds, especially elements in Gropus 1 and 2 Different physical properties At room temperatures: Flourine and chlorine are gases, bromine is a liquid, iodine and astatine are solids Ex: Group 1 – Some metals – lithium, sodium, potassium, for example – react violently with water Horizontal row in the periodic table = period Properties of elements change in a predictable way from one end of a period to the other Ex: Period 3 = elements on far left are metals, far right are nonmetals Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Trends in the Periodic Table An element’s position in the table can give information about that element Ions form by an atom gaining or losing electrons Atoms of elements on the left side of the table form positive ions Group 1 atoms lose an electron to form ions 1+ Group 2 atoms lose two electrons to form ions 2+ Group 18 atoms normally do not form ions Group 17 often form ions 1- Group 16 often form ions 2- Groups 3 through 12 all form positive ions with varying charges Sizes of atoms vary across periods and within groups Size affects how the atom will react with another atom Densities follow a pattern Generally increases from top of a group to the bottom Within a period, elements at the left and right sides are the least dense, the middle are the most dense Ex: Osmium (Os) has the highest known density Trends are a valuable tool, though exact size or density of an atom cannot be predicted exactly Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties