Ch. 9 Inorganic Analysis: Forensic Determination of Metals and Gunshot Residue Flashcards
atomic absorption spectrophotometry (AAS)
a quantitative analysis technique that measures absorption of light by vaporized elements in a sample
atomic mass unit
the sum of the number of protons and the number of neutrons in the nucleus of an atom
atomic number
the number of protons in the nucleus of an atom of an element
compound
a substance formed by the chemical combination of two or more elements in fixed proportions
continuous spectrum
a pattern in which one color of light merges into the next color that is produced when white light is passed through a prism
electromagnetic radiation (EMR)
a general term the is used to describe energy that is encountered daily
electron
a subatomic particle with a negative charge of one (-1) and negligible mass
element
a fundamental building block of matter that cannot be decomposed into a simpler substance by ordinary chemical means
energy-dispersive x-ray
a technique that measures the energy of X-rays emitted in the scanning electron microscope
energy level
any several regions surrounding the nucleus of an atom in which the electrons move
excited state
the state of an atom in which an electron has acquired energy to move to a higher energy level
frequency
the number of crests that pass a fixed point in 1 sec
- 1Hz = frequency of 1 cycle (passage of 1 complete wave) per second
ground state
the state of an atom in which all of its electrons are their lowest possible energy levels
group
one of the vertical columns of elements in the periodic table
gunshot residue (GSR)
material discharged from a firearm other than the bullet
inductively coupled plasma (ICP)
a high-energy argon plasma that uses radio-frequency energy
line spectrum
a spectrum produced by an element that appears as a series of bright lines at specific wavelengths, separated by dark bands
metals
malleable elements
- lustrous
- good conductors of heat & electricity
- tend to lose electrons to form positively charged ions
modified Greiss test
a test for the presence of nitrites in gunshot residue
molecule
the smallest unit of a compound that retains the characteristics of that compound
neutron
an electrically neutral subatomic particle found in the nuclei of atoms
neutron activation analysis (NAA)
an analysis method that bombards the sample with neutrons and then measures the isotopes produced
nonmetals
elements that lack the properties of metals
nucleus
the small, dense, positively charged central core of an atom
- composed of protons & neutrons
orbital
the sublevels of principal energy levels (s, p, d & f)
period
one of the horizontal rows of elements in the periodic table
periodic table
the elements arranged in order of atomic number
- each element has a unique atomic number
plasma
a high temperature gas that has a portion of its atoms ionized which makes the gas capable of conducting electricity
principal energy level
one of the energy levels to which electrons are limited
proton
a subatomic particle with a relative positive charge of (+1) and a mass of 1
- a hydrogen ion
quantum
the smallest increment of radiant energy that may be absorbed or emitted
scanning electron microscopy with energy-dispersive X-ray (SEM-EDX)
the preferred method for the detection of GSR
- investigator applies an adhesive tape directly to the suspect’s hands (or other surface) to lift the GSR
semimetal (metalloid)
elements with properties that lie between those of metals and nonmetals
wavelength
the distance between adjacent wave crests
- usually measured in nanometers (nm)
X-ray fluorescence spectrometry (XRF)
a technique that measures the emission of an x-ray when a sample is exposed to higher-energy X-rays
- energy of the emitted X-ray indicates which element released it
The building blocks from which all matter is constructed are called _______.
atoms
Substances that are composed of 2 or more elements are called _______.
compound
The number of naturally occurring elements is ________.
98
A molecule is a combination of _________ or more elements.
2
A proton has a(n) ________ charge.
positive
The nucleus of an atom is composed of ________ and ________.
protons & neutrons
The atomic number indicates the number of _________ in the nucleus.
protons
In a neutral atom, the number of protons is equal to the number of _________.
neutrons
The periodic table is divided into 18 vertical columns called _______.
groups
Elements within a group on the periodic table have similar _______ properties.
physical & chemical
The elements that are good conductors of electricity and heat and have a shiny appearance are called _______.
metals
Elements that do not conduct heat or electricity are called ________.
nonmetals
White light from an incandescent light bulb, when passed through a prism, produces a(n) ________ spectrum.
continuous
An element that is placed in a flame emits light that, when passed through a prism, produces a(n) _________ spectrum.
line
The alkali metals (Group 1A) all have ________ electron(s) in their outermost energy levels.
1
The halogens (Group VIIA) all have ________ electron(s) in their outermost energy levels.
7
The three metals most commonly used for fabricating everyday objects are _______, _________, and _______.
iron
aluminum
copper
________ are mixtures of metals that are created to have properties that are more desirable than those of their components.
alloys
Glass is composed mostly of the elements _______ and _______.
–
A(n) _________ is a mixture of gases that conduct electricity.
–
The X-ray beam of the XRF strikes a(n) ________-shell electron, which causes it to be ejected.
–
The XRF measures the composition of the _________ of the sample.
–
Collecting GSR for AAS analysis involves the use of swabs containing ________ that are rubbed on the skin of the head.
–
The atomic absorption spectrometer uses a(n) _______ furnace to vaporize the collected GSR.
–
The collection of gunshot residue for the scanning electron microscope analysis uses a(n) _______ ________ to pick the GSR from the skin.
–
A scanning electron microscope operates on the same principle as the light microscope but uses ________ rather than light to illuminate the sample.
–
In SEM, some of the electrons striking the surface cause _________ to be emitted.
–
By measuring the energy of the X-rays emitted in SEM, the identity and amount of each ________ on the GSR can be determined.
–
The incomplete combustion of gunpowder releases a nonmetal ________.
nitrile (NO2)
