Unit C: Exploring Matter Chapter 6: Elements and the Periodic Table 6.1: Atoms and Elements pg. 210 Key Concepts: 1. Elements cannot be broken into simpler substances. 2. Elements of the same column (group) of the periodic table have similar properties. 3. Atoms consist of protons and neutrons in the central core surrounded by electrons. Parts of the Atom Proton: a positively charged particle in an atom. Neutron: a particle in an atom that has no electrical charge. Electron: is a negatively charged particle found in an orbit outside the nucleus of an atom. An atom contains three kinds of sub atomic particles. The protons (positively charged) and the Neutrons (neutral charge) are found within the nucleus of the atoms. The Electrons (negatively charged) are found orbiting the nucleus of the atom. The mass of the atom is found within the nucleus, each of the protons and neutrons have the same mass.
Electrons have very little mass, and are found orbiting the nucleus, but also create the volume of the atom. An atom has a neutral charge. Therefore there are an equal number of protons to electrons, creating a balance. One positively charged proton for each negatively charged electron. Table 1: Particles in an Atom. Particle Charge Location Symbol Name Proton Positive + Nucleus p + Neutron No charge Nucleus n 0 Electron Negative - Orbit e - Figure 1: This model of a fluorine atom shows that it has 9 protons (9 p + ), 9 electrons (blue dots), and 10 neutrons (10 n o ). There are 2 electrons (2 e - ) in the first orbit and 7 electrons in the second orbit (7 e - ).
Electron Orbits (Electron Energy Shells) Electrons are found in the orbits (Electron shells) outside the nucleus. The first orbit (shell) can only contain 2 electrons. The second orbit (shell) can contain 8 electrons, a long with the third orbit. The Importance of Organizations Organizing the Elements: On the Periodic Table Element: is a pure substance that cannot be broken down into simpler substances, either physically or chemically. Periodic Table: the table that lists all the known elements in rows and columns based on patterns of similar properties. All matter is made up of elements. Gold, copper, and oxygen are examples of elements. Each element is made up of only one type of particle or atom. Gold and copper have different properties because they are made up of different types of atoms. Gold is made up of gold atoms and copper is made up of copper atoms. Scientist record data in tables, the elements are recorded in a periodic table, which organizes and arranges the elements with similar properties in groups or families.
The Modern Periodic Table Atomic Number: is the number of protons in an atom of an element; each element has a different atomic number. Period: is a horizontal row in the periodic table of elements. Group or Chemical Family: is a vertical column in the periodic table of elements. The elements found in the periodic table are arranged in order of the number of protons they contain in their nucleus. The number of protons for each element is known as the Atomic Number. Each element has its own atomic number. Figure 4: The atomic number is at the top left-hand corner of each element on the periodic table.
- Each element in the periodic table has its own box. In the box is the element s chemical symbol, name, and atomic number. - The first letter of every chemical symbol is a capital letter. (N for Nitrogen) If there is a second letter, it is lowercase. (Ne for Neon) - Each row of the periodic table is called a Period. The properties of the elements that are in the same period can be very different. - The elements are also placed in columns according to how their electrons are arranged. Each column in the periodic table is called a group or chemical family. Elements in the same group have the same properties. Within each group, all atoms have the same number of electrons in their outer most orbits, or electron shells. (Valence Electrons) - Most elements are either metals (blue boxes) or nonmetals (pink boxes). They are separated by a dark line that looks like a staircase. Hydrogen is the only exception. Elements along the staircase have properties in between those of metals and non-metals. These elements are called metalloids (green boxes).
Figure 3: The elements of the periodic table are arranged in rows (also called periods) and columns. Each group of elements has similar properties. Chemical Families The structure of the atoms explains why elements have similarities and difference. Group 1: Alkali metals, consists of elements below hydrogen, in the first column of the periodic table. Lithium (Li), sodium (Na), potassium (K) and other elements have only one electron found in their outer electron shell or orbit. They will react the same, during chemical reactions.
Group 2: Elements in group 2 are called Alkaline Earth Metals. Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra), all contain two electrons in their outer electron shells or orbits. They will react the same, during chemical reactions. Periodic Trends Elements in the same group or family share some chemical and physical properties and also in their reactivity. Group 1 is more reactive then group 2. On the right side of the periodic table, group 17 (Halogens) is more reactive then group 16. Group 16 is more reactive then group 15.
Figure 5: These elements react in a similar way because each atom has one electron in its outermost electron orbit. Check Your Learning: Questions 1 11, pg. 217 Wrap Up: - Protons and neutrons are found in the nucleus of the atom. Electrons orbit the nucleus. - Protons are positively charged and have about the same mass as neutrons, which have no charge. Electrons are negatively charged and have very little mass compared to protons and neutrons. - The numbers of protons and electrons in an atom are equal. The positive and negative charges cancel each other out, giving the atom a neutral charge. - Elements cannot be broken down into simpler substances. - The elements in the periodic table are in order by increasing atomic number. - Elements in the same group have similar properties.