Ch 02 HW http session masteringbiology com myct assignmentPrintView Ch 02 HW Due 1 00pm on Monday September 23 2013 You will receive no credit for items you complete after the assignment is due Grading Policy Atomic Number and Mass Number Learning Goal To understand the relationship between atomic number and mass number Atoms are described by an atomic number and a mass number The atomic number is the number of protons in the nucleus The mass number represents the sum of the protons and the neutrons in the nucleus If the number of negative electrons is equal to the number of positive protons then the atom is neutral If the number of protons and electrons are not equal then the atom will have a charge For example a phosphorus ion with 15 protons 17 neutrons and 18 electrons would have an atomic number of 15 a mass number of 32 and a charge of 3 Part A What is the mass number of an ion with 106 electrons 159 neutrons and a 1 charge Express your answer as an integer Hint 1 Determine the number of protons How many protons does this ion have Express your answer as an integer Hint 1 How to approach the problem A 1 charge means that the number of protons exceeds the number of electrons by one ANSWER 107 Hint 2 Define mass number Which of the following is equal to the mass number ANSWER 1 of 22 9 21 13 8 17 PM Ch 02 HW http session masteringbiology com myct assignmentPrintView protons neutrons protons neutrons protons neutrons protons neutrons protons electrons ANSWER 266 Correct Activity Electron Arrangement Click here to complete this activity Then answer the questions Part A The innermost electron shell of an atom can hold up to electrons ANSWER 2 of 22 9 21 13 8 17 PM Ch 02 HW http session masteringbiology com myct assignmentPrintView 18 1 32 2 8 Correct This is the maximum number of electrons that can occupy the innermost electron shell Part B Which of these relationships is true of an uncharged atom ANSWER The number of protons is equal to the number of electrons The number of electrons is equal to the number of neutrons The atomic mass is equal to the number of electrons The atomic mass is equal to the atomic number The number of neutrons is equal to the number of protons Correct In this situation the number of positive charges is equal to the number of negative charges Part C What determines the types of chemical reactions that an atom participates in ANSWER its atomic mass the number of electrons in the innermost electron shell the number of electrons in the outermost electron shell its atomic number the number of protons it contains 3 of 22 9 21 13 8 17 PM Ch 02 HW http session masteringbiology com myct assignmentPrintView Correct An atom is least likely to participate in a reaction when its outermost shell is stable Activity Structure of the Atomic Nucleus Click here to complete this activity Then answer the questions Part A What is the atomic number of an atom that has 6 protons 6 neutrons and 6 electrons ANSWER 0 18 12 1 6 Correct This is an atom of carbon an element with 6 protons Atomic number is the number of protons in an atom Part B Which of these refers to atoms with the same atomic number but different atomic masses ANSWER 4 of 22 9 21 13 8 17 PM Ch 02 HW http session masteringbiology com myct assignmentPrintView These atoms are isotopes These atoms have different numbers of electrons These atoms are isomers These atoms are different elements These atoms have different numbers of protons Correct Atoms with the same atomic number and different atomic masses are referred to as isotopes Part C Fluorine s atomic number is 9 and its atomic mass is 19 How many neutrons does fluorine have ANSWER 19 28 9 10 81 Correct Atomic mass is equal to the number of protons plus the number of neutrons 19 9 10 Part D An uncharged atom of boron has an atomic number of 5 and an atomic mass of 11 How many protons does boron have ANSWER 0 11 6 5 16 5 of 22 9 21 13 8 17 PM Ch 02 HW http session masteringbiology com myct assignmentPrintView Correct The atomic number is equal to the number of protons Chapter 2 Pre Test Question 4 Part A Changing the number of would change an atom into an atom of a different element Hint 1 Consider the subatomic particle referred to by an element s atomic number ANSWER bonds formed by an atom protons in an atom neutrons in an atom electrons circling the nucleus of an atom particles in the nucleus of an atom Correct Atoms of each element have a unique number of protons within their nuclei Changing the number of protons in an atom occurs only in nuclear reactions not chemical reactions Chapter 2 Pre Test Question 5 Part A The atoms of different phosphorus isotopes Hint 1 Think about the ways atoms of the same element can have different atomic masses ANSWER 6 of 22 9 21 13 8 17 PM Ch 02 HW http session masteringbiology com myct assignmentPrintView have different numbers of protons react differently with other atoms have different numbers of electrons have different numbers of neutrons have different atomic numbers Correct The phosphorus atom is defined by its proton number Changes in neutron number alter the mass of the atom but not its chemical behavior or reactivity Chapter 2 Pre Test Question 6 Part A The type of bonding and the numbers of covalent bonds an atom can form with other atoms is determined by Hint 1 Consider what portion of an atom would first come into contact with another atom ANSWER the number of protons the number of neutrons the size of the atom smaller atoms are chemically more reactive the number of unpaired electrons in the valence shell the nucleus Correct The fullness of the valence shell determines the pattern of covalent bonding or ionization The reactivity of an atom is a function of the presence of unpaired electrons in one or more orbitals of their valence shells Activity Covalent Bonds 7 of 22 9 21 13 8 17 PM Ch 02 HW http session masteringbiology com myct assignmentPrintView Click here to complete this activity Then answer the questions Part A What type of bond is joining the two hydrogen atoms ANSWER hydrogen covalent ionic hydrophobic hydrophilic Correct A covalent bond is one in which electron pairs are shared Part B A n refers to two or more atoms held together by covalent bonds ANSWER 8 of 22 9 21 13 8 17 PM Ch 02 HW http session masteringbiology com myct assignmentPrintView molecule shell ion community isotope Correct A molecule is defined as two or more atoms held together by covalent bonds Part C This atom can form up to