CBB 3.1-CI 2.2
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
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| What are the three main parts of an atom? | protons, electrons, neutrons
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| How do the particles of an atom differ in electric charge? | Protons – positive charge
Electrons – negative charge
Neutrons – neutral charge
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| Why do atoms have no electrical charge even though most of their particles have charges? | here are equal amounts of protons and electrons making the charges balance (neutral)
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| What is the atomic number of an element? | Number of protons in an atom
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| How can an atomic number be used to distinguish one element from another? | Each element can be identified by the number of protons in the
nucleus
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| The atomic number of the isotope nitrogen-15 is 7. How many protons, neutrons, and electrons make up an atom of nitrogen-15? | Protons – 7
Electrons – 7
Neutrons - 8
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| What are the main reasons that scientists use models to study atoms? | Too small
Explain how matter behaves
Explains why most elements react with other elements
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| In what order did Mendeleev arrange the elements in the first periodic table? | In order of increasing atomic mass
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| What pattern did Mendeleev discover when he arranged the elements? | Noticed a pattern of properties when he arranged the elements in order of increasing atomic mass
Properties = melting point, density, color, atomic mass, number of chemical bonds
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| Describe two differences between Mendeleev’s periodic table and the modern periodic table. | In order by atomic number not atomic mass
New elements have been added
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| List three kinds of information about an element that can be found in a square of the periodic table. | Element’s name
Chemical symbol
Atomic number
Atomic mass
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| Why aren’t the atomic masses of most elements whole numbers? | The atomic mass is an average mass based on the combined percentages of all the isotope of an element.
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| What does an element’s location in the periodic table tell you about that element? | Information about its properties
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| What are VALENCE ELECTRONS? | Electrons that are in the outer shell with the highest energy level and held most loosely.
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| What role do valence electrons play in the formation of compounds from elements? | Valence electrons are most likely to be involved in chemical bonding. When elements react to form compounds, valence electrons may be transferred from one atom to another or shared between atoms.
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| Do oxygen molecules become more or less stable when oxygen forms compounds? EXPLAIN. | When oxygen atoms form compounds, they gain or share valence electrons to make a set of eight valence electrons.
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| Summarize how the periodic table is organized. Use the words PERIOD and GROUP. | A row of elements across the periodic table is called a period. Atomic number and number of valence electrons increase by one from left to right across a period. Elements in the same column are called a group or family.
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| Why do the properties of the elements change in a regular way across the period? | The properties of elements change in a regular way across a period because the number of valence electrons changes regularly.
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| How reactive are the elements in Group 18? EXPLAIN this reactivity in terms of the number of valence electrons. | The elements in Group 18 are the least reactive elements in the periodic table because they have eight valence electrons.
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| What are two basic ways in which ions form from atoms? | Atoms can lose or gain electrons
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| Contrast sodium and chloride ions, including how they form. Write a symbol for each ion. | A sodium ion (Na+) forms when an atom loses one electron and becomes positively charged. A chloride ion (Cl-) forms when a chlorine atom gains one electron and becomes negatively charged.
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| What holds the ions together in sodium chloride? Indicate the specific charges that are involved. | n ionic bond holds the ions together. The sodium ion has a charge of 1+ and the chloride ion has a charge of 1-.
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| What information is given by the formula of an ionic compound? | The ratio of the positive ions to negative ions.
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| The formula for sodium sulfide is Na2S. EXPLAIN what the formula means. | Sodium sulfide consists of two sodium ions and one sulfide ion.
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| Write the formula for calcium chloride. EXPLAIN how you determined this formula. | The formula for CaCl2 because two chloride ions (Cl1-) are needed to balance out the one calcium ion (Ca2+)
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| List three PROPERTIES of ionic compounds | Ionic compounds are hard, brittle crystals that have a high melting point and can conduct electricity when melted or in solution.
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| Relate each property (Ionic compounds are hard, brittle crystals that have a high melting point and can conduct electricity when melted or in solution.) to the characteristics of ionic bonds. | are strong due to the attraction between oppositely charged ions makes crystals of ionic compounds hard and brittle causes compounds to have high melting points ions are charged they can conduct electricity when the compound is melted or dissolved
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| What is the attraction that holds two covalently bonded atoms together? | The attraction of each atom’s nucleus for the shared electrons.
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| A carbon atom can form four covalent bonds. How many valence electrons does it have? | four
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| What is a double bond? Use Figure 24 (in textbook) to explain how a carbon dioxide molecule has a stable set of eight valence electrons for each atom. | A double bond is a bond in which two atoms share two pairs of electrons. This gives each atom a stable set of eight valence electrons.
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| How are the properties of molecular compounds different from those of ionic compounds? | The melting and boiling points of molecular compounds are lower than those of ionic compounds and molecular compounds do not conduct electricity well.
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| Why are most molecular compounds poor conductors of electricity? | Because they do not have charged particles to carry a current.
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| How do some atoms in covalent bonds become slightly negative or slightly positive? What TYPE of covalent bonds do these atoms form? | Some atoms in covalent bonds become slightly negative or positive when they pull more or less strongly on shared electrons. These atoms form polar covalent compounds.
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| Predict whether carbon dioxide or water would have a higher boiling point. EXPLAIN your prediction in terms of the attractions between the molecules. | Water would have a higher boiling point because the attraction between its polar molecules requires more energy to overcome.
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| What is the difference between the physical properties and the chemical properties of a substance? | Physical properties are those that can be observed without changing the substances into another substance.
Chemical properties are those that can be observed only when the substance is changed into another substance.
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