Biology Chapter 2 Flashcards

Study Notes

Parts of the Atom

Nucleus: dense, positively charged core
Electrons: negatively charged particles (-1) orbiting the nucleus
Protons: positively charged particles (+1) located within the nucleus
Neutrons: neutral particles within the nucleus, may be present or absent
Atoms are electrically neutral with equal numbers of protons and electrons

Mass

Mass measures the quantity of matter; a proton's mass serves as a standard unit called dalton or atomic mass unit (amu)
Proton or neutron mass: 1 dalton (1.7 x 10^-24 grams); electron mass: negligible (9 x 10^-28 grams)

Electrons' Contribution

Electrons have negligible mass but are crucial in forming stable atomic associations

Elements and Properties

Elements are pure substances with one type of atom characterized by unique mass and interaction properties

Bohr Model

Visual representation of the helium atom illustrating electron paths around the nucleus

Abundance of Elements

98% of the mass of living organisms is made up of six elements: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur

Importance of Specific Elements

Sodium and potassium: essential for nerve function
Calcium: serves as a biological signal
Iodine: component of vital hormones
Magnesium: bound to chlorophyll in plants

Atomic Notation

Atomic number: unique count of protons in an atom's nucleus, defining each element
Mass number: total number of neutrons and protons in an atom's nucleus; hydrogen typically has one neutron

Isotopes

Isotopes of the same element differ in neutron count but share the same proton number
Most isotopes are stable

Hydrogen Isotopes

Hydrogen-1: 1 proton, 0 neutrons
Deuterium: 1 proton, 1 neutron
Tritium: 1 proton, 2 neutrons

Carbon Isotopes

Carbon-12: 6 protons, 6 neutrons
Carbon-13: 6 protons, 7 neutrons
Carbon-14: 6 protons, 8 neutrons

Atomic Weight

Average of mass numbers of naturally occurring isotopes of an element
Example: Carbon has an atomic weight of 12.011

Radioisotopes and Uses

Unstable isotopes that emit radiation (alpha, beta, gamma) from the nucleus
Released energy can change the number of protons, transforming the element
Applications include labeling molecules, dating fossils, and medical uses (e.g., Cobalt-16 for cancer treatment)

Electrons Functions and Locations

Electrons dictate atomic behavior and reactivity through chemical reactions
Location is defined by orbitals, where electrons are found 90% of the time

Orbitals and Shells

Electrons arranged in shells, each with specific shapes and orientations
Maximum of 2 electrons per orbital; energy level increases with distance from the nucleus
First shell has one s orbital; second shell accommodates up to 8 electrons through 4 orbitals (1 s and 3 p orbitals)

Effect of Electron Position

Filling occurs from lowest to highest energy levels, with stability achieved when outermost shells have eight electrons (valence shell)
Unpaired electrons in the outer shell indicate potential reactivity of the atom

Examples of Stable Electrons

Atoms like helium, neon, and argon possess full outer electron shells ensuring chemical stability

Atomic Reactions

Atoms attain stability through sharing, gaining, or losing electrons, leading to stable bonds with other atoms

Description

Dive into the fundamental concepts of biology with these flashcards from Chapter 2. This study aid highlights essential terms like parts of the atom and mass, providing clear definitions to help reinforce your understanding of atomic structure. Perfect for quick reviews or enhancing your biological knowledge!