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All of the above are True
- Part of the Bohr model proposed that electrons in the hydrogen atom are located in "stationary states" or particular orbits around the nucleus.
- An orbital is the volume in which we are most likely to find an electron.
- The uncertainty principle states that we can never know both the exact location and speed of an electron.
- The emission spectrum of a particular element is always the same and can be used to identify the element.
The Ph scale measures the acidity or alkalinity of water soluble substances (pHstands for 'potential of Hydrogen'). A pH value is a number from 1 to 14, with 7 as the middle (neutral) point. Values below 7 indicate acidity which increases as the number decreases, 1 being the most acidic.
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The study reported here presents a comparative screening of three medicinal plants including oregano (Origanum vulgare L.), lavender (Lavandula angustifolia) and lemon balm (Melissa officinalis) having the same geographical origin, the Southeast region of Romania, and growing in the same natural conditions. The contents of total phenolics and total flavonoids for the extracts of these were determined. Furthermore, the total antioxidant capacity was also evaluated. It was found that Origanum vulgare and Melissa officinalis extracts present the most effective antioxidant capacity in scavenging DPPH radicals, while Lavandula angustifolia is less active. High performance liquid chromatography-mass spectrometry analysis was used to identify the components of extracts. Major phenolic acids identified in the analysed species were ferulic, rosmarinic, p-coumaric and caffeic, while predominant flavonoids were quercetin, apigenin kaempherol, which were present as glucosides.
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