Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
WHAT IS MATTER? A BRIEF REVIEW OF THE CLASSIFICATION, PROPERTIES, AND SEPARATION OF MATTER MIND CATALYST • For each image on page 19: • Categorize the substance as either an element, a compound, or a mixture. • Briefly explain why you categorized it the way you did. • Draw a particle diagram that describes your categorization. What does an element look like on the molecular level? What about a compound or a mixture? Use labels if necessary. • If the substance is undergoing a process, explain whether it is a physical or chemical process. Justify your answer. MIND CATALYST ATOMIC STRUCTURE AND THE PERIODIC TABLE MODERN VIEW OF ATOMIC STRUCTURE AND PERIODIC TABLE TRENDS A SUMMARY OF THE MODERN VIEW OF THE ATOM • The atom consists of positive, negative, and neutral entities (protons, electrons, and neutrons) • Protons and neutrons are located in the nucleus of the atom, which is small • Protons determine element’s identity • There can be a variable number of neutrons for the same number of protons – isotopes! • Isotopes have the same number of protons but different numbers of neutrons • Electrons are located outside of the nucleus • Electrons determine element’s chemical properties NUCLEUS SIZE VS. ELECTRON CLOUD SIZE • Most of the volume of the atom is due to electrons MASSES OF THE PROTON, NEUTRON, ELECTRON • Most of the mass of the atom is due to the protons and neutrons within the nucleus IMPORTANT DEFINITIONS TO KNOW • Atomic number (Z) • Number of protons in the nucleus • Mass number (A) • Total number of nucleons in the nucleus (i.e., protons and neutrons) • Isotopes have the same Z but different A! ISOTOPES OF CARBON ATOMIC MASS VS. MASS NUMBER • Look on your periodic table at the mass of carbon • The red number is NOT the mass number!! • It is the average atomic mass of ALL isotopes of carbon that are known to exist • One atomic mass unit is equal to 1.66 x 10-24 grams, which is 1/12th the mass of a 12C atom • So, the element carbon on the periodic table is actually a mixture of the isotopes carbon-12, carbon-13, and carbon-14 • Therefore, the atomic mass on the periodic table is a weighted average of the atomic mass of all isotopes of that particular element CALCULATING AVERAGE ATOMIC MASS FOR AN ELEMENT • One can calculate the average atomic weight of an element if the abundance of each isotope for that element is known Average Atomic Mass % natural abundance = ∙ atomic mass1 100 1 % natural abundance + ∙ atomic mass2 … 100 2 ATOMS, ELEMENTS, AND THE PERIODIC TABLE • The Periodic Table is used to organize the 114 elements in a meaningful way • Arranged by increasing atomic number THE PERIODIC TABLE A BRIEF REVIEW OF THE ORGANIZATION OF THE PERIODIC TABLE • Columns in the periodic table are called groups • Numbered from 1A to 8A or 1 to 18 • Atoms with similar properties appear in groups or families • They are similar because they all have the same number of valence (outer shell) electrons, which governs their chemical behavior • Remember, valence electrons are electrons in the highest-numbered sand p- orbitals! • Rows in the periodic table are called periods • Elements of the same period have the same number of energy levels • As you move across a period, the number of electrons and protons increases, leading to increase in atomic number • Elements within the same period do not generally show similarity in properties, except d-block and f-block (lanthanides) elements FAMILIES OF THE PERIODIC TABLE • Some of the groups in the periodic table are given special names, and are called families • These names indicate the similarities of chemical properties between group members as a result of same number of valence electrons: • • • • • Group 1:Alkali metals Group 2: Alkaline earth metals Group 16: Chalcogens Group 17: Halogens Group 18: Noble gases A BRIEF REVIEW OF THE ORGANIZATION OF THE PERIODIC TABLE • Metals are located on the left hand side of the Periodic Table • Most of the elements are metals • Non-metals are located in the top right hand side of the Periodic Table • Elements with properties similar to both metals and non-metals are called metalloids and are located at the interface between the metals and nonmetals USING THE PERIODIC TABLE TO PREDICT ION CHARGE • The number of electrons an atom loses or gains is related to its position on the periodic table • Metals tend to form cations whereas non-metals tend to form anions WHAT IS A CATION? • When an atom or molecule loses electrons, it becomes positively charged • For example, when Na loses an electron it becomes Na+ • Positively charged ions are called cations WHAT IS AN ANION? • When an atom or molecule gains electrons, it becomes negatively charged • For example when Cl gains an electron it becomes Cl• Negatively charged ions are called anions • An atom / molecule can lose or gain more than 1 electron!